The Flat Earth Society

Flat Earth Discussion Boards => Flat Earth Community => Topic started by: Gulliver on May 25, 2014, 09:26:54 AM

Title: Newton's Laws of Motion
Post by: Gulliver on May 25, 2014, 09:26:54 AM
There's a recurring theme of ignorance in the upper forums regarding Newton's Laws of Motion. His first major work, Philosophia naturalis principia mathematica, describes three fundamental laws of motion. The concept that FEer seem to struggle to handle and properly apply is acceleration. Even TheEngineer used to argue that acceleration was relative. It is not. Location is relative since there is no intrinsic coordinate system. Velocity is relative. In the thought experiment with two ships, altogether alone in the Universe, passing each other, observers on each ship can't determine which ship is in motion.

However, you know whether you're accelerating. You feel the force involved. You feel your weight on Earth. You fell the merry-go-round pulling you towards its center. You feel the airplane turning, rising, or dropping. So the argument that planes just "fly around" to delay their arrival fails quickly: The passengers would feel (and see) the turns and bust the required conspiracy.

Another problem FEers tend to have is trying to bash noobs with the circumnavigation argument. FEers argue that you can travel "around" the Earth, say on the Equator by traveling due east. Yes, on the FE that's a curved path, but you'd travel a curved path if you flew due east on the RE too. This fails: the passengers can detect the curved path. The pilot must steer the rudder to maintain the curved path. They would break the conspiracy. (Oh, and no, it's not a curved path on the RE, ignored changing in altitude. One needs only remember that a straight line on the surface of sphere follows the surface, just like the plane would. Indeed on an RE, the pilots and passenger would not feel any "curvature".)

One more lesson for this post: the term acceleration should be used carefully, in its scientific context. For example, to Thorks's slow acceptance, you can travel away from something, yet accelerate towards it. The ISS, for example, accelerates toward the gravitational center of the RE but never travels towards it. To Tom Bishop's chagrin, acceleration is the change in velocity, in speed, direction, or both. It does not mean going fast (or slow).
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 12:04:29 PM
There's a recurring theme of ignorance in the upper forums regarding Newton's Laws of Motion. His first major work, Philosophia naturalis principia mathematica, describes three fundamental laws of motion. The concept that FEer seem to struggle to handle and properly apply is acceleration. Even TheEngineer used to argue that acceleration was relative. It is not. Location is relative since there is no intrinsic coordinate system. Velocity is relative. In the thought experiment with two ships, altogether alone in the Universe, passing each other, observers on each ship can't determine which ship is in motion.
You are aware that most of Newton's work was actually related to alchemy and that you are just picking and choosing the things you like from his studies? And then you start talking about relativity. Newton was not the founder of those theories.

However, you know whether you're accelerating. You feel the force involved. You feel your weight on Earth. You fell the merry-go-round pulling you towards its center. You feel the airplane turning, rising, or dropping. So the argument that planes just "fly around" to delay their arrival fails quickly: The passengers would feel (and see) the turns and bust the required conspiracy.
No, they wouldn't. When you train as a pilot, one fun lesson involves a blindfold. Your instructor will pull you all over the sky, and ask you to recover. The really good instructors can make you feel like you are descending when you are actually upside down and climbing. Please do some research before stating 'facts'. Your misinformation makes our forum look like an argument over a beer, not a fascinating homage to science.
https://en.wikipedia.org/wiki/The_leans
^ Read that to understand why a passenger and even pilot have no idea from forces what their body is doing. Its one of the first things pilots learn, because if they don't trust their instruments over their senses, it is often fatal.

Another problem FEers tend to have is trying to bash noobs with the circumnavigation argument. FEers argue that you can travel "around" the Earth, say on the Equator by traveling due east. Yes, on the FE that's a curved path, but you'd travel a curved path if you flew due east on the RE too. This fails: the passengers can detect the curved path. The pilot must steer the rudder to maintain the curved path. They would break the conspiracy. (Oh, and no, it's not a curved path on the RE, ignored changing in altitude. One needs only remember that a straight line on the surface of sphere follows the surface, just like the plane would. Indeed on an RE, the pilots and passenger would not feel any "curvature".)
Are you suggesting that passengers would feel rudder (you don't turn with rudder, you yaw ... but anyway) to make a correction of 24859/360 = roughly one degree heading change every 70 miles?
You would only need to set a bank angle of roughly 0.06 degrees at 550 mph. 0.06 degrees is absolutely imperceptible. With wind and turbulence a pilot would not have a clue they were doing this.

One more lesson for this post: the term acceleration should be used carefully, in its scientific context.
Lesson? You've been wrong about absolutely everything so far.

For example, to Thorks's slow acceptance, you can travel away from something, yet accelerate towards it. The ISS, for example, accelerates toward the gravitational center of the RE but never travels towards it.
The ISS doesn't accelerate. Its in low earth orbit at a constant speed of around 17000mph To have a force of acceleration in one direction and an opposing force that cancels that out in the opposite direction does not mean one is accelerating. If I get in my car and accelerate to 150mph before the wind resistance is so great my car stops accelerating doesn't mean I am still accelerating. It means I am now at 150mph and that is that as the forces balanced.
You are confusing angular velocity with angular acceleration.
https://en.wikipedia.org/wiki/Angular_velocity

I find it hard to understand from my tens of thousands of posts that you would pick one from your example, and its one where you don't get it. not one where I have been wrong. I mean I must have been wrong at some point in that time, so how did you end up with that example?
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 25, 2014, 12:50:46 PM
Let's start slow. You seem to again need help with basic grade-school physics. Let's consider here:
The ISS doesn't accelerate. Its[sic] in low earth orbit at a constant speed of around 17000mph.
Please recall your grade school physics. Acceleration is a change in magnitude, direction, or both of an object's velocity. Your point about a constant speed (magnitude) is not sufficient to support your claim that "t]he ISS doesn't accelerate." The ISS's velocity changes direction constantly, so the ISS constantly accelerates. Once you understand this, let me know and we can consider your other points. Just to check your proper understanding, ask yourself in what direction does the ISS accelerate and why? Thanks!
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 12:53:42 PM
The ISS's velocity changes direction constantly, so the ISS constantly accelerates.
No, ClockTower, it doesn't.

https://en.wikipedia.org/wiki/Angular_velocity
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 25, 2014, 01:09:45 PM
The ISS's velocity changes direction constantly, so the ISS constantly accelerates.
No, ClockTower, it doesn't.

https://en.wikipedia.org/wiki/Angular_velocity
Please tell me then what the ISS's velocity was at 0 UTC and 1 UTC this morning. You argue that the velocity was the same, right? Why didn't the ISS leave orbit then? Why didn't the mutual attraction between the ISS and the RE cause the ISS to fall towards their center of gravity?
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 01:15:39 PM
Because it has an angular velocity.

It doesn't need to be accelerating to change direction constantly.

https://en.wikipedia.org/wiki/Angular_acceleration
is something else entirely. The ISS is not accelerating. This is why its speed and angular displacement remain constant.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 25, 2014, 01:26:56 PM
Because it has an angular velocity.

It doesn't need to be accelerating to change direction constantly.

https://en.wikipedia.org/wiki/Angular_acceleration
is something else entirely. The ISS is not accelerating. This is why its speed and angular displacement remain constant.
Did you really just post that an object need not accelerate to change direction? Amazing!

You can convince me of your point in two ways: 1) Provide a reference that says something with angular velocity cannot accelerate linearly. or 2) Explain how the ISS stays in orbit without being accelerated constantly towards the RE. Spoiler alert: I've seen you lose this point in the archives in the old site. I laughed reading it weeks ago and did not expect to get a second round of laughs today. Thanks!
Title: Re: Newton's Laws of Motion
Post by: jroa on May 25, 2014, 01:46:59 PM
I thought Newton's physics were proven wrong more than one hundred years ago?  It is still taught in school because of its child like simplicity. 
Title: Re: Newton's Laws of Motion
Post by: Rama Set on May 25, 2014, 01:55:18 PM
Jroa, if you knew that, then you would also know that Newton's physics are incredibly accurate at almost all scales. They are much simpler than QM and Einsteinian relativity, so they are still an incredibly valuable and accurate tool.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 02:45:00 PM
Because it has an angular velocity.

It doesn't need to be accelerating to change direction constantly.

https://en.wikipedia.org/wiki/Angular_acceleration
is something else entirely. The ISS is not accelerating. This is why its speed and angular displacement remain constant.
Did you really just post that an object need not accelerate to change direction? Amazing!

You can convince me of your point in two ways: 1) Provide a reference that says something with angular velocity cannot accelerate linearly. or 2) Explain how the ISS stays in orbit without being accelerated constantly towards the RE. Spoiler alert: I've seen you lose this point in the archives in the old site. I laughed reading it weeks ago and did not expect to get a second round of laughs today. Thanks!
1) I didn't say it had to. But acceleration is a rate of change. Velocity is not.
2) No, I got bored of the debate last time as I am becoming now, because the people I was debating with weren't very good at physics. I already explained how a constant force of acceleration does not necessarily yield constant acceleration of the body in question using the car/wind resistance argument. The ISS is not constantly accelerating. It is in a stable orbit (assuming orbit exists - but another argument for another day) by virtue of all those forces being balanced. If it was accelerating it would either speed up or fail to remain in its orbit. It has a constant angular velocity.
Title: Re: Newton's Laws of Motion
Post by: inquisitive on May 25, 2014, 03:00:58 PM
I drive at 30mph round a corner.   Am I accelerating?
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 03:03:23 PM
I drive at 30mph round a corner.   Am I accelerating?
Assuming you are already in the corner at 30mph and you have no intention of every turning out of it (like a satellite) then no.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 25, 2014, 03:13:10 PM
Because it has an angular velocity.

It doesn't need to be accelerating to change direction constantly.

https://en.wikipedia.org/wiki/Angular_acceleration
is something else entirely. The ISS is not accelerating. This is why its speed and angular displacement remain constant.
Did you really just post that an object need not accelerate to change direction? Amazing!

You can convince me of your point in two ways: 1) Provide a reference that says something with angular velocity cannot accelerate linearly. or 2) Explain how the ISS stays in orbit without being accelerated constantly towards the RE. Spoiler alert: I've seen you lose this point in the archives in the old site. I laughed reading it weeks ago and did not expect to get a second round of laughs today. Thanks!
1) I didn't say it had to. But acceleration is a rate of change. Velocity is not.
2) No, I got bored of the debate last time as I am becoming now, because the people I was debating with weren't very good at physics. I already explained how a constant force of acceleration does not necessarily yield constant acceleration of the body in question using the car/wind resistance argument. The ISS is not constantly accelerating. It is in a stable orbit (assuming orbit exists - but another argument for another day) by virtue of all those forces being balanced. If it was accelerating it would either speed up or fail to remain in its orbit. It has a constant angular velocity.
So is the ISS constantly changing the direction of its motion? Isn't changing direction of motion one form of acceleration?
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 25, 2014, 03:15:55 PM
I drive at 30mph round a corner.   Am I accelerating?
Assuming you are already in the corner at 30mph and you have no intention of every turning out of it (like a satellite) then no.
Where does the intent of an object come into the definition of acceleration? (BTW great point, inquisitive!)
Title: Re: Newton's Laws of Motion
Post by: inquisitive on May 25, 2014, 03:22:36 PM
I drive at 30mph round a corner.   Am I accelerating?
Assuming you are already in the corner at 30mph and you have no intention of every turning out of it (like a satellite) then no.
How would you calculate acceleration?  Knowing the units are m/s/s (in metric).  And the formula v^2 = u^2 + 2as.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 03:24:31 PM
Because it has an angular velocity.

It doesn't need to be accelerating to change direction constantly.

https://en.wikipedia.org/wiki/Angular_acceleration
is something else entirely. The ISS is not accelerating. This is why its speed and angular displacement remain constant.
Did you really just post that an object need not accelerate to change direction? Amazing!

You can convince me of your point in two ways: 1) Provide a reference that says something with angular velocity cannot accelerate linearly. or 2) Explain how the ISS stays in orbit without being accelerated constantly towards the RE. Spoiler alert: I've seen you lose this point in the archives in the old site. I laughed reading it weeks ago and did not expect to get a second round of laughs today. Thanks!
1) I didn't say it had to. But acceleration is a rate of change. Velocity is not.
2) No, I got bored of the debate last time as I am becoming now, because the people I was debating with weren't very good at physics. I already explained how a constant force of acceleration does not necessarily yield constant acceleration of the body in question using the car/wind resistance argument. The ISS is not constantly accelerating. It is in a stable orbit (assuming orbit exists - but another argument for another day) by virtue of all those forces being balanced. If it was accelerating it would either speed up or fail to remain in its orbit. It has a constant angular velocity.
So is the ISS constantly changing the direction of its motion? Isn't changing direction of motion one form of acceleration?
ffs. angular velocity. What is wrong with you?
Title: Re: Newton's Laws of Motion
Post by: spaceman spiff on May 25, 2014, 06:16:13 PM
Wait, so an obect in circular motion with constant angular speed is not accelerating? Is this what Thork is saying? Wow...
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 25, 2014, 06:23:56 PM
The ISS doesn't accelerate.

http://en.wikipedia.org/wiki/Angular_acceleration
Quote
Angular acceleration is the rate of change of angular velocity.

http://en.wikipedia.org/wiki/Angular_velocity
Quote
In physics, the angular velocity is defined as the rate of change of angular displacement and is a vector quantity (more precisely, a pseudovector) which specifies the angular speed (rotational speed) of an object and the axis about which the object is rotating.

http://en.wikipedia.org/wiki/Acceleration
Quote
Acceleration, in physics, is the rate at which the velocity of an object changes over time.

http://en.wikipedia.org/wiki/Velocity
Quote
Velocity is the rate of change of the position of an object, equivalent to a specification of its speed and direction of motion, e.g. 60 km/h to the north[...]Velocity is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is called "speed"[...]

The ISS has a velocity (magnitude and direction).  It's velocity vector changes due to the force of gravity.  This change caused by the force of gravity is known as acceleration.

More info: https://www.khanacademy.org/science/physics/newton-gravitation/gravity-newtonian/v/acceleration-due-to-gravity-at-the-space-station

Seriously, take one physics class if you want to argue about physics.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 06:40:42 PM
http://en.wikipedia.org/wiki/Angular_acceleration
Quote
Angular acceleration is the rate of change of angular velocity.
This is what I have been trying to say. If angular velocity remains the same (as in a stable orbit), then there is no rate of change hence no acceleration.

This seems like a very easy topic for you to grasp.
Title: Re: Newton's Laws of Motion
Post by: spaceman spiff on May 25, 2014, 06:54:03 PM
http://en.wikipedia.org/wiki/Angular_acceleration
Quote
Angular acceleration is the rate of change of angular velocity.
This is what I have been trying to say. If angular velocity remains the same (as in a stable orbit), then there is no rate of change hence no acceleration.

This seems like a very easy topic for you to grasp.
Nice job cherry picking garygreen's post. You can say that there's no angular acceleration, but not that there's no acceleration. From garygreen's post:
Quote
Acceleration, in physics, is the rate at which the velocity of an object changes over time.
Quote
Velocity is the rate of change of the position of an object, equivalent to a specification of its speed and direction of motion, e.g. 60 km/h to the north[...]Velocity is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is called "speed"[...]
Since the velocity vector of the ISS changes direction, it is therefore accelerating
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 07:07:52 PM
http://en.wikipedia.org/wiki/Angular_acceleration
Quote
Angular acceleration is the rate of change of angular velocity.
This is what I have been trying to say. If angular velocity remains the same (as in a stable orbit), then there is no rate of change hence no acceleration.

This seems like a very easy topic for you to grasp.
Nice job cherry picking garygreen's post. You can say that there's no angular acceleration, but not that there's no acceleration. From garygreen's post:
Quote
Acceleration, in physics, is the rate at which the velocity of an object changes over time.
Quote
Velocity is the rate of change of the position of an object, equivalent to a specification of its speed and direction of motion, e.g. 60 km/h to the north[...]Velocity is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is called "speed"[...]
Since the velocity vector of the ISS changes direction, it is therefore accelerating
I am saying that the ISS is not accelerating.

I am sat in my chair. Under RET that means I have a force of acceleration towards the ground at 9.81 m/s^2.
But I'M NOT ACCELERATING ANYWHERE. At t=0 I am sat in my chair and at t=5 minutes I'm still in the exact same spot. There has been no rate of change at all.  Having a force of acceleration applied to me doesn't mean I am accelerating. The forces are cancelled. I'm stationary. The ISS has its forces cancelled. It travels with a constant angular velocity. Its not accelerating anywhere.

I got bored of this the last time. I'm getting bored again. Feel free to say how I was completely wrong about everything again next time you want to try to discredit me. Somehow my running out of patience over simple concepts is deemed as my not understanding something. But to me it just proves what a bunch of disingenuous little trolls you are.
Title: Re: Newton's Laws of Motion
Post by: spaceman spiff on May 25, 2014, 07:21:08 PM
http://en.wikipedia.org/wiki/Angular_acceleration
Quote
Angular acceleration is the rate of change of angular velocity.
This is what I have been trying to say. If angular velocity remains the same (as in a stable orbit), then there is no rate of change hence no acceleration.

This seems like a very easy topic for you to grasp.
Nice job cherry picking garygreen's post. You can say that there's no angular acceleration, but not that there's no acceleration. From garygreen's post:
Quote
Acceleration, in physics, is the rate at which the velocity of an object changes over time.
Quote
Velocity is the rate of change of the position of an object, equivalent to a specification of its speed and direction of motion, e.g. 60 km/h to the north[...]Velocity is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is called "speed"[...]
Since the velocity vector of the ISS changes direction, it is therefore accelerating
I am saying that the ISS is not accelerating.

I am sat in my chair. Under RET that means I have a force of acceleration towards the ground at 9.81 m/s^2.
But I'M NOT ACCELERATING ANYWHERE. At t=0 I am sat in my chair and at t=5 minutes I'm still in the exact same spot. There has been no rate of change at all.  Having a force of acceleration applied to me doesn't mean I am accelerating. The forces are cancelled. I'm stationary. The ISS has its forces cancelled. It travels with a constant angular velocity. Its not accelerating anywhere.

I got bored of this the last time. I'm getting bored again. Feel free to say how I was completely wrong about everything again next time you want to try to discredit me. Somehow my running out of patience over simple concepts is deemed as my not understanding something. But to me it just proves what a bunch of disingenuous little trolls you are.
I didn't even mention forces in my post, but whatever. Just to make sure we are in the same page, please define acceleration. I feel like we are not agreeing on the basics.
As a side note, what other force is acting on the ISS besides gravity?
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 07:26:10 PM
How about you read the thread then, and not jump in at the end shouting the odds?
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 25, 2014, 07:56:41 PM
I am saying that the ISS is not accelerating.
I think you're just confusing speed and velocity.  Speed is a scalar quantity.  It is described only by magnitude.  The speed of the ISS is constant.

Velocity is a vector quantity.  It is always described by magnitude and direction.  The direction component of the ISS' velocity changes as it orbits due to the force of gravity.  This is acceleration.  Any change in an objects' velocity is acceleration.

I am sat in my chair. Under RET that means I have a force of acceleration towards the ground at 9.81 m/s^2.
But I'M NOT ACCELERATING ANYWHERE. At t=0 I am sat in my chair and at t=5 minutes I'm still in the exact same spot. There has been no rate of change at all.  Having a force of acceleration applied to me doesn't mean I am accelerating. The forces are cancelled. I'm stationary. The ISS has its forces cancelled. It travels with a constant angular velocity. Its not accelerating anywhere.

The ISS is not resting on a chair resting on the Earth's surface.  The force of gravity is not cancelled out by anything.  That's what we're trying to tell you.  It's always freely falling toward the Earth because of the force of gravity.  This force is not cancelled out.  It changes the direction of the ISS' velocity vector.  That's acceleration.

The ISS doesn't stay in orbit because the force of gravity is cancelled out.  The force of gravity acts on the ISS and causes it to accelerate in the direction of the Earth's surface. 

(http://upload.wikimedia.org/wikipedia/commons/4/4e/Orbital_motion.gif)

Look at how the velocity vector is constantly changing direction.

http://en.wikipedia.org/wiki/Orbit#Understanding_orbits
Quote
There are a few common ways of understanding orbits:

-As the object moves sideways, it falls toward the central body. However, it moves so quickly that the central body will curve away beneath it.

-A force, such as gravity, pulls the object into a curved path as it attempts to fly off in a straight line.

-As the object moves sideways (tangentially), it falls toward the central body. However, it has enough tangential velocity to miss the orbited object, and will continue falling indefinitely. This understanding is particularly useful for mathematical analysis, because the object's motion can be described as the sum of the three one-dimensional coordinates oscillating around a gravitational center.

Notice that all of these descriptions involve acceleration due to gravity.  Gravity alters the velocity vector.  That's what acceleration is.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 08:00:52 PM
Christ on a bike. I know their is an acceleration due to gravity in the RET model. I also know that angular acceleration is a vector quantity and not a scalar. BUT THE ISS IS NOT ACCELERATING! It has an angular velocity. Not an angular acceleration. Why are you being so obtuse?
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 25, 2014, 08:42:40 PM
BUT THE ISS IS NOT ACCELERATING! It has an angular velocity.

These two sentences cannot both be true.

Again, http://en.wikipedia.org/wiki/Angular_velocity
Quote
angular velocity is defined as the rate of change of angular displacement

Angular velocity is the rate at which the direction component of a velocity vector changes over time.  Acceleration is the rate at which a velocity vector changes over time.  Angular velocity requires acceleration.

Exactly what we've been trying to tell you from the beginning is that the ISS could not have any angular velocity without a force causing it to accelerate in the direction of the Earth's surface.  Angular velocity is a quantity that describes how much its velocity vector changes over time.
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 25, 2014, 08:59:58 PM
Or consider the following reductio:

Let's assume that you're correct that the ISS is not accelerating.  That means, by definition, that its velocity vector does not change.  So, if the ISS is above the Earth with some velocity, and if that velocity does not change, then, per Newton's 1st, it will move at a constant speed and direction until some force acts on it.  The trajectory of the ISS would look like this:

(http://i.imgur.com/VrOxEyC.png)

It would have to.  If the velocity vector doesn't change, then the path of the ISS will always be a straight line in the direction of its velocity.

Since its path is elliptical and not a straight line, its velocity must change.  Any change in velocity over time is acceleration.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 09:13:31 PM
Exactly what we've been trying to tell you from the beginning is that the ISS could not have any angular velocity without a force causing it to accelerate in the direction of the Earth's surface.  Angular velocity is a quantity that describes how much its velocity vector changes over time.
I am not disputing that there is a component of acceleration. I'm saying the ISS itself is not accelerating. The forces balance.
Read the bloody thread.
Title: Re: Newton's Laws of Motion
Post by: inquisitive on May 25, 2014, 09:14:29 PM
Some numbers please.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 09:18:44 PM
Some numbers please.
4, 303, 42, 232, 2.

Numbers of what?
Title: Re: Newton's Laws of Motion
Post by: inquisitive on May 25, 2014, 09:43:40 PM
Some numbers please.
4, 303, 42, 232, 2.

Numbers of what?
What is the acceleration of the ISS?
Title: Re: Newton's Laws of Motion
Post by: spaceman spiff on May 25, 2014, 09:55:26 PM
Exactly what we've been trying to tell you from the beginning is that the ISS could not have any angular velocity without a force causing it to accelerate in the direction of the Earth's surface.  Angular velocity is a quantity that describes how much its velocity vector changes over time.
I am not disputing that there is a component of acceleration. I'm saying the ISS itself is not accelerating. The forces balance.
Read the bloody thread.
Which forces? Gravity and...? Also, if there's a non-zero component of the acceleration (as you may have implied by "there is a component of acceleration"), it means that the ISS is accelerating.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 09:59:43 PM
Some numbers please.
4, 303, 42, 232, 2.

Numbers of what?
What is the acceleration of the ISS?
0.
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 25, 2014, 10:55:02 PM
I am not disputing that there is a component of acceleration. I'm saying the ISS itself is not accelerating. The forces balance.
Read the bloody thread.

That doesn't make sense.  Please clarify.  The ISS can't be accelerating and not accelerating.

I think the problem is that you're using 'acceleration' and 'angular acceleration' interchangeably.  They don't mean the same thing.  Angular acceleration is a change in angular velocity.  Acceleration is a change in any velocity vector.  Speaking of reading the thread, this entire discussion could have been avoided by you reading my first post in this thread that contains these definitions. 

The ISS has a constant angular velocity (no angular acceleration).  It does not have a constant velocity.  Those are different things.  Its speed is constant.  Its velocity is not.  This is because the ISS is being accelerated by the force of gravity in the direction of the Earth's surface, as per all of the sources I've cited.  This is the very definition of an orbit.  It couldn't stay in orbit without being accelerated toward the surface of the Earth.

The OP was exactly right, and you basically just proved his point with your posts in this thread.  You just don't have any concept that acceleration means a specific thing and has a specific definition.  It doesn't just mean 'going faster.'  And it means something different from angular acceleration.  Just as angular velocity means something different than velocity.  You're just mixing up all these terms and definitions and then acting like everyone else is an idiot for not knowing that you're doing that.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 11:07:28 PM
I can't be any more specific. I'm sat in my chair. I'm not accelerating anywhere. t=0 is the same as t=15 seconds.
There is a force of acceleration exerted on me, But I'M NOT ACCELERATING.
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 25, 2014, 11:34:05 PM
I can't be any more specific.

You could start by using the correct words to describe the correct things.

I'm sat in my chair. I'm not accelerating anywhere. t=0 is the same as t=15 seconds.
There is a force of acceleration exerted on me, But I'M NOT ACCELERATING.

You experience no acceleration in the direction of the Earth's surface because you are resting on a chair.  The force of the chair opposes equally the force of gravity.  The ISS is not resting on a chair.  There is no force opposing the force of gravity for the ISS.  Again, if there were, then the ISS could not be in orbit.  I don't think you actually read my posts.  I've explained this like five times now.  You're just like PP.  You just read a couple of sentences and skip over responding to the substance of what anyone says.  Just hit reply and start typing something.  And you think for some reason that it's a mark of intelligence.  You're fucking weird.

There isn't a legitimately licensed pilot on the planet who could possibly have this kind of trouble applying and speaking intelligently about Newton's laws.  Get out with that nonsense.  What a joke. 

e: you also don't seem to get what an inertial frame of reference is, which would also be super troubling if you were actually a licensed pilot.  You are not accelerating toward the surface of the Earth when seated (or accelerating at all in your local, rotating inertial frame.  Everything around you is moving at the same rate under the same forces).  But, you are being accelerated in a non-rotating inertial frame (say, from the point of view of someone looking at the whole Earth from a stationary position in space).  Your velocity vector changes as you rotate around the globe on the Earth's surface.  Just as with the ISS, if it didn't, then you would travel at a constant speed and direction and fly off the surface as it fell away below you.

Any change in the direction or magnitude of a velocity vector is called acceleration.  By definition.  That's what the word means.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 25, 2014, 11:39:37 PM
I can't be any more specific. I'm sat in my chair. I'm not accelerating anywhere. t=0 is the same as t=15 seconds.
There is a force of acceleration exerted on me, But I'M NOT ACCELERATING.
How about answer the simple question:

Is the ISS's velocity (note: not asking about angular velocity) changing direction at any point in its orbit? Thanks.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 25, 2014, 11:45:07 PM
There is no force opposing the force of gravity for the ISS.
Ok, great. Now I know why you are having so much trouble with your basic physics. You don't know what centripetal force is.

(http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/orvl.gif)

Cool. Go look it up, and come back a better debater. I'm gonna call time on this debate. its really dull and has nothing to do with earth's shape. Til next time ... Thork out.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 26, 2014, 12:00:28 AM
There is no force opposing the force of gravity for the ISS.
Ok, great. Now I know why you are having so much trouble with your basic physics. You don't know what centripetal force is.

(http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/orvl.gif)

Cool. Go look it up, and come back a better debater. I'm gonna call time on this debate. its really dull and has nothing to do with earth's shape. Til next time ... Thork out.
Would you do that diagram again please, this time with only real forces? Thanks! Reference: https://answers.yahoo.com/question/index?qid=20100619084420AAl0nDP
Title: Re: Newton's Laws of Motion
Post by: Thork on May 26, 2014, 12:08:04 AM
lol. yahoo answers. My source was http://hyperphysics.phy-astr.gsu.edu/hbase/orbv.html

note the .edu
An educational website. Not a bunch of dumb teens unqualified to answer the questions asked.
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 26, 2014, 12:09:26 AM
centripetal force

DING DING DING DING DING WE HAVE A WINNER!!!!  Welcome to the point I've been making this whole time.  But you seem to think centripetal force opposes gravity?  Gravity is the centripetal force.  You'd know that if you read the links your image came from instead of just being like 'yo dude check out these maths cool huh they totally prove my point for some reason.'

http://hyperphysics.phy-astr.gsu.edu/hbase/orbv.html#co
Quote
Gravity supplies the necessary centripetal force to hold a satellite in orbit about the earth.

http://hyperphysics.phy-astr.gsu.edu/hbase/cf.html#cf
Quote
Any motion in a curved path represents accelerated motion, and requires a force directed toward the center of curvature of the path.

But please, keep asserting your asinine misconceptions with absolute confidence.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 26, 2014, 12:25:34 AM
centripetal force

DING DING DING DING DING WE HAVE A WINNER!!!!  Welcome to the point I've been making this whole time.  But you seem to think centripetal force opposes gravity.  Gravity is the centripetal force.  You'd know that if you read the links your image came from instead of just being like 'yo dude check out these maths cool huh they totally prove my point for some reason.'

http://www.mwit.ac.th/~physicslab/hbase/orbv.html
Quote
Gravity supplies the necessary centripetal force to hold a satellite in orbit about the earth.

http://www.mwit.ac.th/~physicslab/hbase/cf.html#cf
Quote
Any motion in a curved path represents accelerated motion, and requires a force directed toward the center of curvature of the path.

But please, keep asserting your asinine misconceptions with absolute confidence.

How about you take a reading comprehension test.
Quote from: http://www.mwit.ac.th/~physicslab/hbase/orbv.html
Setting the gravity force from the universal law of gravity equal to the required centripetal force yields the description of the orbit.

I'll make it easy as you don't like reading.

(http://www.reformation.org/geostationary-satellite3.jpg)
source: http://www.reformation.org/geostationary-satellites.html

Note the satellite has an opposite and equal force to gravity.

Anyway, can we put his to bed. I would like to go too. Its 1:30am.
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 26, 2014, 01:08:10 AM
Just admit that you're wrong.  Your own source says directly and explicitly that you are wrong.  "Any motion in a curved path represents accelerated motion, and requires a force directed toward the center of curvature of the path."  The ISS follows a curved path.  All of the credible evidence in this thread, including your own sources, explicitly concur with what I've been saying since my first post in this thread.

(http://www.reformation.org/geostationary-satellite3.jpg)
source: http://www.reformation.org/geostationary-satellites.html

That diagram is showing centrifugal force, which isn't a real force and doesn't keep satellites in orbit.  It also manages to get that wrong.  Centrifugal force cannot explain the orbit of the ISS in a rotating reference frame.  It's just a mathematical tool to describe objects in a non-inertial reference frame as if they were in an inertial reference frame.

http://en.wikipedia.org/wiki/Centrifugal_force_(rotating_reference_frame)
Quote
Analysis of motion within rotating frames can be greatly simplified by the use of the fictitious forces. By starting with an inertial frame, where Newton's laws of motion hold, and keeping track of how the time derivatives of a position vector change when transforming to a rotating reference frame, the various fictitious forces and their forms can be identified. Rotating frames and fictitious forces can often reduce the description of motion in two dimensions to a simpler description in one dimension (corresponding to a co-rotating frame). In this approach, circular motion in an inertial frame, which only requires the presence of a centripetal force, becomes the balance between the real centripetal force and the frame-determined centrifugal force in the rotating frame where the object appears stationary.

It's also different from centripetal force, which is what you were talking about originally.  Dunno why we're talking about centrifugal forces now.

Oh, and your source talking about centrifugal force is both incorrect and incredible:

http://www.reformation.org/page2.html
http://www.reformation.org/stationary-earth.html
http://www.reformation.org/antichrist.html
http://www.reformation.org/lincoln-conspiracy-solved-at-last.html

Weren't you just criticizing another user for offering sources that weren't scientifically credible?  Do you think this religious website counts as credible or reliable?

e: I'm getting my inertial/non-inertial/rotating reference frames mixed up in my head, so I'm not sure I'm getting those relations right in relation to centrifugal force.  The point is that it's a fictitious force that doesn't actually describe how a satellite stays in orbit.

Oh look more physicists saying exactly what I'm been saying to you this whole time: http://math.ucr.edu/home/baez/physics/General/Centrifugal/centri.html
Quote
After this fine start, von Braun then proceeds to muddy the water.  He says that as the bullet is shot at ever faster speeds, "its trajectory will be less deflected because the centrifugal force is increased by its higher speed, and more effectively counteracts the Earth's gravitational pull."  At this point physicists baulk.  Centrifugal force?  What has that got to do with satellite motion?
[...]
In an inertial frame, if there really were two equal-but-opposite forces on the satellite as von Braun drew them, then the total force on it would be zero.  So it wouldn't accelerate; it would move in a straight line with constant speed.  Since the orbiting satellite doesn't move in a straight line, neither von Braun's picture nor his explanation can be right.
[...]
In reality, nothing holds the Moon up.  As Newton's inertial frame analysis predicts, the Moon is completely under gravity's thrall; in other words, it falls, because in such a frame there's only one force on the Moon: gravity.  Gravity accelerates it.  That doesn't mean its speed must necessarily change, or that it must get closer to Earth (although actually both of these things do occur slightly during the month, but that's not an important point).  If Newton's F=ma is solved for the general case of falling under gravity, the motions that result are lines, circles, ellipses, parabolae, and hyperbolae.  In one of those great correspondences between Nature and pure mathematics, these are precisely the curves that result if we take a cone and slice it in any direction.

Even if the Moon's orbit were circular, its direction of travel would still be changing, which is one kind of acceleration.  (Remember that acceleration is a change in velocity, meaning that acceleration can change an object's speed, or it can change merely the direction of motion, or both.)

It's practically a word-for-word summary of my arguments.  Do you have anything other than some random religious website to support your argument?
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 26, 2014, 02:42:32 AM
lol. yahoo answers. My source was http://hyperphysics.phy-astr.gsu.edu/hbase/orbv.html

note the .edu
An educational website. Not a bunch of dumb teens unqualified to answer the questions asked.
Odd, I though FEers wanted everyone to consider the argument, its reasoning, and its basis, not from what website it originates. Oh well, I guess the appeal-to-authority fallacy is strong in this one. (But I do lament that pp hasn't raced in to admonish Thork to reconsider.)

I see that others have successfully explained the nature of centripetal force to you using other sources, so I'll just encourage the awesomeness of garygreen for now.
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 26, 2014, 07:01:33 PM
How about you take a reading comprehension test.
Quote from: http://www.mwit.ac.th/~physicslab/hbase/orbv.html
Setting the gravity force from the universal law of gravity equal to the required centripetal force yields the description of the orbit.

I missed this yesterday, and I can't pass it up.  This sentence agrees with me.  It says that the description of an orbit comes from setting the force of gravity equal to the required centripetal force.  Equal to.  No opposed to.  As we just learned (from your own source), centripetal force is applied toward the center of curvature.

Every single statement from this source that you provided is in direct opposition to your argument, and in exact alignment with mine.

Just look at the maths you provided.

(http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/orvl.gif)

This describes exactly what I've been saying to you.  The very first term is "Fgravity = Fcentripetal".  It's a force equation.  Nothing in these maths is showing a canceling out of the force of gravity.  It describes an accelerating object.  By definition.

Please tell me more about my reading comprehension.
Title: Re: Newton's Laws of Motion
Post by: jroa on May 29, 2014, 12:11:58 PM
The ISS goes at a constant speed.  Look it up.
Title: Re: Newton's Laws of Motion
Post by: markjo on May 29, 2014, 12:31:21 PM
The ISS goes at a constant speed.  Look it up.
Incorrect.  If this were true, then the ISS would not need periodic boosts to its orbit.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 29, 2014, 12:49:10 PM
The ISS goes at a constant speed.  Look it up.
Incorrect.  If this were true, then the ISS would not need periodic boosts to its orbit.
jroa, please read the OP and try to learn some grade school physics. Moving at a constant non-zero speed is not the same as not accelerating. Acceleration involves the change of velocity, a vector with both magnitude (here arguably "speed") and direction. A change in either or both is acceleration. We know the ISS accelerates (as long as it doesn't fly off from Earth as its velocity is constantly changing direction. (Technically and pedantically, I do need to state that I'm assuming a inertial Frame of Reference http://en.wikipedia.org/wiki/Inertial_frame_of_reference in order to say "fly off".)
Title: Re: Newton's Laws of Motion
Post by: inquisitive on May 29, 2014, 04:23:47 PM
The ISS goes at a constant speed.  Look it up.
Incorrect.  If this were true, then the ISS would not need periodic boosts to its orbit.
jroa, please read the OP and try to learn some grade school physics. Moving at a constant non-zero speed is not the same as not accelerating. Acceleration involves the change of velocity, a vector with both magnitude (here arguably "speed") and direction. A change in either or both is acceleration. We know the ISS accelerates (as long as it doesn't fly off from Earth as its velocity is constantly changing direction. (Technically and pedantically, I do need to state that I'm assuming a inertial Frame of Reference http://en.wikipedia.org/wiki/Inertial_frame_of_reference in order to say "fly off".)
What is the value of the acceleration?
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 29, 2014, 06:49:50 PM
The ISS goes at a constant speed.  Look it up.
Incorrect.  If this were true, then the ISS would not need periodic boosts to its orbit.
jroa, please read the OP and try to learn some grade school physics. Moving at a constant non-zero speed is not the same as not accelerating. Acceleration involves the change of velocity, a vector with both magnitude (here arguably "speed") and direction. A change in either or both is acceleration. We know the ISS accelerates (as long as it doesn't fly off from Earth as its velocity is constantly changing direction. (Technically and pedantically, I do need to state that I'm assuming a inertial Frame of Reference http://en.wikipedia.org/wiki/Inertial_frame_of_reference in order to say "fly off".)
What is the value of the acceleration?
Approximately: 9.8 m/s2 towards the center of the Earth. See: http://en.wikipedia.org/wiki/Standard_gravity
Title: Re: Newton's Laws of Motion
Post by: Pete Svarrior on May 29, 2014, 07:22:55 PM
Approximately: 9.8 m/s2 towards the center of the Earth. See: http://en.wikipedia.org/wiki/Standard_gravity
Surely it would be considerably less than that, given that the ISS is quite much farther away from the Earth. A brief calculation based on Newton's law of universal gravitation (https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation) suggests something more akin to 8.7m/s2.
Title: Re: Newton's Laws of Motion
Post by: Pete Svarrior on May 29, 2014, 07:23:48 PM
For a more detailed explanation:

https://www.youtube.com/watch?v=R5CRZONOHCU

Probably worth noting that you could have gotten the same result from the picture already posted here:

(http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/orvl.gif)

Using very rough estimates (because I'm lazy) of REarth = 6300km and rISS = 6700km, we get the following gorbit:

%5Cleft%28%20%5Cfrac%7B6300%5Cleft%5Bkm%5Cright%5D%7D%7B6700%5Cleft%5Bkm%5Cright%5D%7D%20%5Cright%29%5E2%5Ctimes%209.8%5Cleft%5B%5Cfrac%7Bm%7D%7Bs%5E2%7D%5Cright%5D%20%3D%208.66%5Cleft%5B%5Cfrac%7Bm%7D%7Bs%5E2%7D%5Cright%5D
Title: Re: Newton's Laws of Motion
Post by: spoon on May 29, 2014, 07:46:20 PM
Why would you consider the linear motion of an object when it is oh-so-obviously in an orbit (according the the RE model)? ???

Thork is right. The ISS has constant angular velocity, ergo no acceleration.
Title: Re: Newton's Laws of Motion
Post by: Thork on May 29, 2014, 08:51:32 PM
Why would you consider the linear motion of an object when it is oh-so-obviously in an orbit (according the the RE model)? ???

Thork is right. The ISS has constant angular velocity, ergo no acceleration.
Forget it. They can't be that stupid. I think I got trolled for 2 pages. :-(
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 29, 2014, 09:58:36 PM
Approximately: 9.8 m/s2 towards the center of the Earth. See: http://en.wikipedia.org/wiki/Standard_gravity
Surely it would be considerably less than that, given that the ISS is quite much farther away from the Earth. A brief calculation based on Newton's law of universal gravitation (https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation) suggests something more akin to 8.7m/s2.
I highlighted the word you may have missed.

Oh, and just to help you with your physics your forgot to specify the direction of your accelerations.

Hey Thork, pizzaplanet not only agrees with me that the ISS accelerates but provides a non-zero magnitude for it. I guess you consider him a troll now too, right?

Why would you consider the linear motion of an object when it is oh-so-obviously in an orbit (according the the RE model)? ???

Thork is right. The ISS has constant angular velocity, ergo no acceleration.
Please do tell me the reason that an object having a constant angular velocity means that it has a constant linear velocity. (This is what you're arguing, right?) Thanks.
Title: Re: Newton's Laws of Motion
Post by: garygreen on May 29, 2014, 10:05:24 PM
Why would you consider the linear motion of an object when it is oh-so-obviously in an orbit (according the the RE model)? ???

Thork is right. The ISS has constant angular velocity, ergo no acceleration.

Ergo no angular acceleration.  Any curved motion through space is accelerated motion.  In a non-rotating frame, the path of the ISS is curved.  Acceleration must be happening.

Forget it. They can't be that stupid. I think I got trolled for 2 pages. :-(

You haven't been trolled.  You're just not correct that the ISS isn't accelerating.  And you haven't brought to bear a single source that disagrees with my assessment.

Here are more sources that agree with me and say virtually word-for-word what I've been saying to you in this thread:

http://www.gravity.phys.uwm.edu/~doqui/doqui/209-5.pdf
Quote
An object revolving in a circle is continuously accelerating even when the speed remains constant.
http://dev.physicslab.org/Document.aspx?doctype=3&filename=CircularMotion_CentripetalAcceleration.xml
Quote
An object is said to be moving in uniform circular motion when it maintains a constant speed while traveling in a circle. Remember that since acceleration is a vector quantity comprised of both magnitude and direction, objects can accelerate in any of these three ways:
 
       1. constant direction, changing speed (linear acceleration);
       2. constant speed, changing direction (centripetal acceleration);
       3. change in both speed and direction (angular acceleration).
http://www.physicsclassroom.com/mmedia/circmot/ucm.cfm
Quote
An object moving in a circle is accelerating. Accelerating objects are objects which are changing their velocity - either the speed (i.e., magnitude of the velocity vector) or the direction. An object undergoing uniform circular motion is moving with a constant speed. Nonetheless, it is accelerating due to its change in direction. The direction of the acceleration is inwards.
http://www.sparknotes.com/physics/dynamics/uniformcircularmotion/section1.rhtml
Quote
Because the direction of a particle moving in a circle changes at a constant rate, it must experience uniform acceleration.
http://web.utk.edu/~cnattras/Physics221Spring2013/modules/m5/uniform_circular_motion.htm
Quote
An object moving in a circle of radius r with constant speed v is accelerating.  The direction of its velocity vector is changing all the time, but the magnitude of the velocity vector stays constant.  The acceleration vector cannot have a component in the direction of the velocity vector, since such a component would cause a change in speed.  The acceleration vector must therefore be perpendicular to the velocity vector at any point on the circle.  This acceleration is called radial acceleration or centripetal acceleration, and it points towards the center of the circle.

Title: Re: Newton's Laws of Motion
Post by: spoon on May 30, 2014, 12:11:01 AM
Please do tell me the reason that an object having a constant angular velocity means that it has a constant linear velocity. (This is what you're arguing, right?) Thanks.
Not at all what I am arguing. If you can't tell, you aren't worth the effort.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 01:32:54 AM
Please do tell me the reason that an object having a constant angular velocity means that it has a constant linear velocity. (This is what you're arguing, right?) Thanks.
Not at all what I am arguing. If you can't tell, you aren't worth the effort.
So you got nothing. Thanks for trying though.
Title: Re: Newton's Laws of Motion
Post by: Pete Svarrior on May 30, 2014, 01:50:39 AM
Approximately: 9.8 m/s2 towards the center of the Earth. See: http://en.wikipedia.org/wiki/Standard_gravity
Surely it would be considerably less than that, given that the ISS is quite much farther away from the Earth. A brief calculation based on Newton's law of universal gravitation (https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation) suggests something more akin to 8.7m/s2.
I highlighted the word you may have missed.
So you consider 8.7m/s2 to be "approximately" 9.8m/s2. In other words, an error margin of 12% is perfectly acceptable to you. Well, I suppose that tells us a lot about your understanding of grade school physics. I shall update my sig to reflect that.

Y'know, I was concerned when the two results I lazily (and drunkenly, admittedly) provided were <0.5% off from one another. I guess that was completely unfounded, since I could have easily been over 24 times that off without causing any objections from you.

Keeping that in mind, saying that the acceleration applied to objects on the Earth is 11m/s^2 should necessarily be fine with you as well. The implications are just amazing.

Oh, and just to help you with your physics your forgot to specify the direction of your accelerations.
Yes, because that's definitely relevant when one's explicitly calculating magnitudes. Get the fuck out of here.

Hey Thork, pizzaplanet not only agrees with me that the ISS accelerates but provides a non-zero magnitude for it.
Yes, Thork is woefully wrong. So are you, having claimed that the ISS is literally on the round Earth's surface (if it's not right now, then the acceleration of 9.8m/s^2 will bring it there very soon, and we should brace for this catastrophic event). It's shameful that you're not willing to acknowledge it. It would have been perfectly fine for you to admit that you mistakenly applied standard gravitation where it obviously shouldn't have been applied, but you lack the honesty to do so. This will be duly noted.

There is no shame in making a novice mistake, even if this very thread had provided you with all the detail you needed prior to making the mistake. You blatantly denying it is what makes it bad.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 02:47:55 AM
Approximately: 9.8 m/s2 towards the center of the Earth. See: http://en.wikipedia.org/wiki/Standard_gravity
Surely it would be considerably less than that, given that the ISS is quite much farther away from the Earth. A brief calculation based on Newton's law of universal gravitation (https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation) suggests something more akin to 8.7m/s2.
I highlighted the word you may have missed.
So you consider 8.7m/s2 to be "approximately" 9.8m/s2. In other words, an error margin of 12% is perfectly acceptable to you. Well, I suppose that tells us a lot about your understanding of grade school physics. I shall update my sig to reflect that.

Y'know, I was concerned when the two results I lazily (and drunkenly, admittedly) provided were <0.5% off from one another. I guess that was completely unfounded, since I could have easily been over 24 times that off without causing any objections from you.

Keeping that in mind, saying that the acceleration applied to objects on the Earth is 11m/s^2 should necessarily be fine with you as well. The implications are just amazing.

Oh, and just to help you with your physics your forgot to specify the direction of your accelerations.
Yes, because that's definitely relevant when one's explicitly calculating magnitudes. Get the fuck out of here.

Hey Thork, pizzaplanet not only agrees with me that the ISS accelerates but provides a non-zero magnitude for it.
Yes, Thork is woefully wrong. So are you, having claimed that the ISS is literally on the round Earth's surface (if it's not right now, then the acceleration of 9.8m/s^2 will bring it there very soon, and we should brace for this catastrophic event). It's shameful that you're not willing to acknowledge it. It would have been perfectly fine for you to admit that you mistakenly applied standard gravitation where it obviously shouldn't have been applied, but you lack the honesty to do so. This will be duly noted.

There is no shame in making a novice mistake, even if this very thread had provided you with all the detail you needed prior to making the mistake. You blatantly denying it is what makes it bad.
You're right. I let an 12% overstatement get into my post that I could have avoided by spending more time explaining where 8.7 m/s2 came from to someone who appears not to even grasp the concept of acceleration. I opted for concept over precision. I do apologize that my choice doesn't suit your likes, but, hey, that's why I read and respond to replies to my posts--to learn. Now, if you could please take the time to explain to Thork why you think that he is woefully wrong, I would bet many would be appreciative. I know I would. Thanks in advance.

Just to be pedantic for a paragraph... Since I used the qualifier "[a]pproximately" and since Standard Gravity is "near", not just "on", the Earth's surface, I did not, as you claim, literally claim the ISS to be on the surface of Earth.  I'm sorry to be pedantic again. I'll try to do a better job avoiding being pedantic.
Title: Re: Newton's Laws of Motion
Post by: juner on May 30, 2014, 02:57:15 AM
You're right. I let an 11% overstatement get into my post that I could have avoided by spending more time explaining where 8.7 m/s2 came from to someone who appears not to even grasp the concept of acceleration. I opted for concept over precision. I do apologize that my choice doesn't suit your likes, but, hey, that's why I read and respond to replies to my posts--to learn. Now, if you could please take the time to explain to Thork why you think that he is woefully wrong, I would bet many would be appreciative. I know I would. Thanks in advance.

I enjoyed how when PP showed how incredibly wrong you were, your only defense was to whine and make excuses.

It is okay to be wrong.  Maybe try learning some humility.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 03:00:37 AM
You're right. I let an 11% overstatement get into my post that I could have avoided by spending more time explaining where 8.7 m/s2 came from to someone who appears not to even grasp the concept of acceleration. I opted for concept over precision. I do apologize that my choice doesn't suit your likes, but, hey, that's why I read and respond to replies to my posts--to learn. Now, if you could please take the time to explain to Thork why you think that he is woefully wrong, I would bet many would be appreciative. I know I would. Thanks in advance.

I enjoyed how when PP showed how incredibly wrong you were, your only defense was to whine and make excuses.

It is okay to be wrong.  Maybe try learning some humility.
Just out of curiosity... do you ever use this alt to provide content, or can we all just put it on the "ignore list"? Thanks.
Title: Re: Newton's Laws of Motion
Post by: juner on May 30, 2014, 03:03:34 AM
You're right. I let an 11% overstatement get into my post that I could have avoided by spending more time explaining where 8.7 m/s2 came from to someone who appears not to even grasp the concept of acceleration. I opted for concept over precision. I do apologize that my choice doesn't suit your likes, but, hey, that's why I read and respond to replies to my posts--to learn. Now, if you could please take the time to explain to Thork why you think that he is woefully wrong, I would bet many would be appreciative. I know I would. Thanks in advance.

I enjoyed how when PP showed how incredibly wrong you were, your only defense was to whine and make excuses.

It is okay to be wrong.  Maybe try learning some humility.
Just out of curiosity... do you ever use this alt to provide content, or can we all just put it on the "ignore list"? Thanks.

I created this alt and made it an administrator so I could purposefully upset you.

I am sorry if the only content I provide is hurting the feelings of angry noobs.  I see you didn't take note of my comment about learning some humility.  Please, continue on being butt hurt.
Title: Re: Newton's Laws of Motion
Post by: Pete Svarrior on May 30, 2014, 03:35:16 AM
You're right. I let an 12% overstatement get into my post that I could have avoided by spending more time explaining where 8.7 m/s2 came from to someone who appears not to even grasp the concept of acceleration. I opted for concept over precision.
In this particular case, you were responding to inquisitive, not Thork. While I have personal disagreements with inquisitive, I do know that he's an RE'er, and I doubt he would have denied that the ISS has an acceleration; so no, you weren't explaining this to someone who doesn't grasp the concept - you were answering a question to someone who was probably appreciative of the concept, and you were answering it incorrectly.

Seriously, sometimes it's easier to just say "okay, I made a mistake" and move on. Everyone makes mistakes sometimes - it only reflects negatively on you when you do everything in your power to deny the mistake (and make further mistakes in doing so).

As for why Thork is wrong - I think others have done a pretty good job at explaining it. Under the round Earth model, it would be impossible for the ISS to stay in orbit if it wasn't accelerating - it would necessarily have to either float away from the Earth or crash right into it. In fact, this would be largely true for a flat Earth as well (although the specifics of the acceleration may vary).
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 04:31:05 AM
I enjoyed how when PP showed how incredibly wrong you were, your only defense was to whine and make excuses.

It is okay to be wrong.  Maybe try learning some humility.
Just out of curiosity... do you ever use this alt to provide content, or can we all just put it on the "ignore list"? Thanks.

I created this alt and made it an administrator so I could purposefully upset you.

I am sorry if the only content I provide is hurting the feelings of angry noobs.  I see you didn't take note of my comment about learning some humility.  Please, continue on being butt hurt.
Thank you. That's what we needed to know. I'll be sure to encourage noobs to read this post and ignore this and any other alts we detect.
You're right. I let an 12% overstatement get into my post that I could have avoided by spending more time explaining where 8.7 m/s2 came from to someone who appears not to even grasp the concept of acceleration. I opted for concept over precision.
In this particular case, you were responding to inquisitive, not Thork. While I have personal disagreements with inquisitive, I do know that he's an RE'er, and I doubt he would have denied that the ISS has an acceleration; so no, you weren't explaining this to someone who doesn't grasp the concept - you were answering a question to someone who was probably appreciative of the concept, and you were answering it incorrectly.

Seriously, sometimes it's easier to just say "okay, I made a mistake" and move on. Everyone makes mistakes sometimes - it only reflects negatively on you when you do everything in your power to deny the mistake (and make further mistakes in doing so).

As for why Thork is wrong - I think others have done a pretty good job at explaining it. Under the round Earth model, it would be impossible for the ISS to stay in orbit if it wasn't accelerating - it would necessarily have to either float away from the Earth or crash right into it. In fact, this would be largely true for a flat Earth as well (although the specifics of the acceleration may vary).
Thank you for explaining this again to Thork (and his alt, spoon). I'm sure he'll try to learn from your post. I assume your comment about dealing with mistakes applies first and foremost to the worst mistake (Thork's) in the thread. As far as my mistake is concerned, I've admitted to it and explained why I choose to make it.

I disagree that every time that I quote someone that I'm replying to only the author of the quote. Surely you expect others to read your posts, right?

Finally, I'd appreciate if in your signature you correctly quote me. I, as any grade school student should do, specified the direction of the vector involved, here: toward the center of the Earth. Thanks again.
Title: Re: Newton's Laws of Motion
Post by: juner on May 30, 2014, 05:05:18 AM
Thank you. That's what we needed to know. I'll be sure to encourage noobs to read this post and ignore this and any other alts we detects.

I am glad you can admit you are nothing more than an angry noob.  Someone shows you where you are wrong, and the best you have is accusing people of being alts.  It is kind of sad, really.  Anyway, best of luck in your other endeavors, as you were thoroughly dismantled here.  Another victory for FE!
Title: Re: Newton's Laws of Motion
Post by: Pete Svarrior on May 30, 2014, 02:30:17 PM
I assume your comment about dealing with mistakes applies first and foremost to the worst mistake (Thork's) in the thread.
No, it doesn't. Thork hasn't made a mistake, he's simply fundamentally wrong about things. You, on the other hand, I suspect were fully aware of Newton's law of universal gravitation, but merely forgot to apply it in this situation, having assumed that 400km wouldn't be enough to make a significant difference. It's a much less serious issue, except for the fact that your continuous dodging and denying of it makes it more serious - there is a difference between making a mistake (and owning up once pointed out), being completely wrong (Thork's case), and being intellectually dishonest (what you've escalated your own case to). Own up, admit a mistake, move on. Simple.

Finally, I'd appreciate if in your signature you correctly quote me. I, as any grade school student should do, specified the direction of the vector involved, here: toward the center of the Earth. Thanks again.
Unfortunately, sigs have limited lengths, and I made sure to include the direction as part of the context. Of course, since the question was about the value (magnitude) of the acceleration, it is inappropriate and needless to specify the direction - magnitudes themselves do not have directions. I'd be happy to include this in my sig to make you look even worse, but, as I said, we limit sigs at 300 characters.

Thank you. That's what we needed to know. I'll be sure to encourage noobs to read this post and ignore this and any other alts we detect.
You may want to acknowledge 2 things:
Ultimately, if you suspect that someone is using alts for sockpuppetting, you should report it in S&C. While having alts is not disallowed here, using them in attempt to benefit oneself in a conversation is (http://forum.tfes.org/index.php?topic=977.0).
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 04:27:07 PM
Thork hasn't made a mistake, he's simply fundamentally wrong about things. You, on the other hand, I suspect were fully aware of Newton's law of universal gravitation, but merely forgot to apply it in this situation, having assumed that 400km wouldn't be enough to make a significant difference. It's a much less serious issue, except for the fact that your continuous dodging and denying of it makes it more serious - there is a difference between making a mistake (and owning up once pointed out), being completely wrong (Thork's case), and being intellectually dishonest (what you've escalated your own case to). Own up, admit a mistake, move on. Simple.

Unfortunately, sigs have limited lengths, and I made sure to include the direction as part of the context. Of course, since the question was about the value (magnitude) of the acceleration, it is inappropriate and needless to specify the direction - magnitudes themselves do not have directions. I'd be happy to include this in my sig to make you look even worse, but, as I said, we limit sigs at 300 characters.

Thank you for that very useful and detailed reply. I learned several important things.

I hope you'll accept some feedback though. I'll try diligently here not to be pedantic or "snarky".

How does Thork claim that the ISS does not accelerate without his making a mistake? Are you saying that if I was merely confused about the importance of a 12% error, I did not make a mistake? Maybe you've confused his mistake of ignorance with my error of judgement.

A vector quantity is clearly defined in mathematics to include both its magnitude and (if the magnitude is non-zero) its direction. No, the value of vector is not just its magnitude. You might find this explanation useful: http://www.physicsclassroom.com/Class/1DKin/U1L1b.cfm , If you will, you should consider your mistake here similar to declaring that the value of a real number is just its absolute value, ignoring its sign.

Please define what you mean by "admitting a mistake". Please contrast it with what I've posted:
You're right. I let an 12% overstatement get into my post that I could have avoided by spending more time explaining where 8.7 m/s2 came from to someone who appears not to even grasp the concept of acceleration. I opted for concept over precision. I do apologize that my choice doesn't suit your likes, but, hey, that's why I read and respond to replies to my posts--to learn.

Again, you really should quote directly, not add "context" yourself. I count that you dropped 32 characters. But, hey, it's not like accurate quoting is essential as long as you get the context right.
Approximately: 9.8 m/s2 towards the center of the Earth.
Again, I found your post helpful. Thanks.
Title: Re: Newton's Laws of Motion
Post by: DuckDodgers on May 30, 2014, 04:52:01 PM
It looks like a few of you missed the portion where thork clearly states it has no angular acceleration, stating that the angular velocity is constant. 
Title: Re: Newton's Laws of Motion
Post by: Rama Set on May 30, 2014, 05:03:55 PM
It looks like a few of you missed the portion where thork clearly states it has no angular acceleration, stating that the angular velocity is constant. 

Thork clearly said:


The ISS doesn't accelerate. Its in low earth orbit at a constant speed of around 17000mph To have a force of acceleration in one direction and an opposing force that cancels that out in the opposite direction does not mean one is accelerating. If I get in my car and accelerate to 150mph before the wind resistance is so great my car stops accelerating doesn't mean I am still accelerating. It means I am now at 150mph and that is that as the forces balanced.
You are confusing angular velocity with angular acceleration.
https://en.wikipedia.org/wiki/Angular_velocity

He said the ISS has no acceleration because it has no Angular acceleration, which is not a true statement.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 05:06:07 PM
It looks like a few of you missed the portion where thork clearly states it has no angular acceleration, stating that the angular velocity is constant.
Please tell me more. Are you saying that Thork meant to say that I was wrong to say that the ISS accelerates (as an example of an object moving in one direction but accelerating in another) because it has no angular acceleration? Surely you'd expect Thork to know the difference between acceleration and angular acceleration before saying that the ISS does not accelerate, right? On the "old site", I believe he claimed to be a laid-off commercial cargo jet co-pilot. Please help me understand your point. Thanks.

It looks like a few of you missed the portion where thork clearly states it has no angular acceleration, stating that the angular velocity is constant. 
Thanks Rama Set for another great post. You bet me to most of the point.

Thork clearly said:


The ISS doesn't accelerate. Its in low earth orbit at a constant speed of around 17000mph To have a force of acceleration in one direction and an opposing force that cancels that out in the opposite direction does not mean one is accelerating. If I get in my car and accelerate to 150mph before the wind resistance is so great my car stops accelerating doesn't mean I am still accelerating. It means I am now at 150mph and that is that as the forces balanced.
You are confusing angular velocity with angular acceleration.
https://en.wikipedia.org/wiki/Angular_velocity

He said the ISS has no acceleration because it has no Angular acceleration, which is not a true statement.
Title: Re: Newton's Laws of Motion
Post by: DuckDodgers on May 30, 2014, 05:22:36 PM
Christ on a bike. I know their is an acceleration due to gravity in the RET model. I also know that angular acceleration is a vector quantity and not a scalar. BUT THE ISS IS NOT ACCELERATING! It has an angular velocity. Not an angular acceleration. Why are you being so obtuse?
I rest my case.  No angular acceleration is clearly his statement.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 05:33:25 PM
Christ on a bike. I know their is an acceleration due to gravity in the RET model. I also know that angular acceleration is a vector quantity and not a scalar. BUT THE ISS IS NOT ACCELERATING! It has an angular velocity. Not an angular acceleration. Why are you being so obtuse?
I rest my case.  No angular acceleration is clearly his statement.
No... He said, "THE ISS IS NOT ACCELERATING". In Science, accelerating is not the same as angular acceleration. Here are links to each defintion:
http://en.wikipedia.org/wiki/Acceleration
http://en.wikipedia.org/wiki/Angular_acceleration

Saying that the ISS is not accelerating because the ISS has a constant angular velocity is like saying you can't be thirsty while swimming in the Pacific Ocean.

Oh, and if I read Thork's misspellings as I think he intended, he argues that the ISS has an acceleration, but isn't accelerating. I think he meant there some other force (centripetal?) providing an opposing acceleration, so the IIS's net acceleration is zero. Go figure.
Title: Re: Newton's Laws of Motion
Post by: DuckDodgers on May 30, 2014, 05:47:25 PM
You clearly did not read thork's post that I quoted.  He blatantly says "it has an angular velocity.  Not an angular acceleration." Thork is clearly right and you refuse to acknowledge that he is.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 05:55:55 PM
You clearly did not read thork's post that I quoted.  He blatantly says "it has an angular velocity.  Not an angular acceleration." Thork is clearly right and you refuse to acknowledge that he is.
I never said either of those two sentences were wrong. (Well, actually I did agree earlier with markjo that due to variations in ISS's orbit it does indeed have times with angular acceleration. So, yes, Thork is wrong even on that, but it's not nearly as bad (or on topic) as saying the ISS does not accelerate.)

To repeat: Thork stated that the ISS does not accelerate. He is wrong.

ETA (in a flippant manner): So are you proposing a new Rule of Engagement. Every time Thork posts a true sentence, I must log on within a day and acknowledge that he is right? Did you want to extend that to all FEers' sentences in all threads and every REer acknowledgement of each true sentence? I think you may be protesting too much there, pal.
Title: Re: Newton's Laws of Motion
Post by: Rama Set on May 30, 2014, 06:48:30 PM
You clearly did not read thork's post that I quoted.  He blatantly says "it has an angular velocity.  Not an angular acceleration." Thork is clearly right and you refuse to acknowledge that he is.

Just to be succinct.  No one is saying that the ISS has angular acceleration.

Thork essentially is saying: "The ISS has no acceleration because it does not have angular accleration."  This is wrong because the ISS has linear acceleration.
Title: Re: Newton's Laws of Motion
Post by: DuckDodgers on May 30, 2014, 06:55:41 PM
He is saying it have no change in angular velocity, hence no angular acceleration.  He has made no claim regarding it in a linear sense.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 06:59:45 PM
He is saying it have no change in angular velocity, hence no angular acceleration.  He has made no claim regarding it in a linear sense.
Wrong. He said:


The ISS doesn't accelerate. Its in low earth orbit at a constant speed of around 17000mph To have a force of acceleration in one direction and an opposing force that cancels that out in the opposite direction does not mean one is accelerating. If I get in my car and accelerate to 150mph before the wind resistance is so great my car stops accelerating doesn't mean I am still accelerating. It means I am now at 150mph and that is that as the forces balanced.
You are confusing angular velocity with angular acceleration.
https://en.wikipedia.org/wiki/Angular_velocity
Rama Set just told you this. Please pay attention.
Title: Re: Newton's Laws of Motion
Post by: DuckDodgers on May 30, 2014, 07:14:55 PM
When speaking of orbit, is a constant speed not a constant angular velocity?  You've really muddied up the whole discussion.
Title: Re: Newton's Laws of Motion
Post by: Rama Set on May 30, 2014, 07:20:47 PM
When speaking of orbit, is a constant speed not a constant angular velocity?  You've really muddied up the whole discussion.

Garygreen provided many sources to elaborate on this.  Please have a boo below:

Why would you consider the linear motion of an object when it is oh-so-obviously in an orbit (according the the RE model)? ???

Thork is right. The ISS has constant angular velocity, ergo no acceleration.

Ergo no angular acceleration.  Any curved motion through space is accelerated motion.  In a non-rotating frame, the path of the ISS is curved.  Acceleration must be happening.

Forget it. They can't be that stupid. I think I got trolled for 2 pages. :-(

You haven't been trolled.  You're just not correct that the ISS isn't accelerating.  And you haven't brought to bear a single source that disagrees with my assessment.

Here are more sources that agree with me and say virtually word-for-word what I've been saying to you in this thread:

http://www.gravity.phys.uwm.edu/~doqui/doqui/209-5.pdf
Quote
An object revolving in a circle is continuously accelerating even when the speed remains constant.
http://dev.physicslab.org/Document.aspx?doctype=3&filename=CircularMotion_CentripetalAcceleration.xml
Quote
An object is said to be moving in uniform circular motion when it maintains a constant speed while traveling in a circle. Remember that since acceleration is a vector quantity comprised of both magnitude and direction, objects can accelerate in any of these three ways:
 
       1. constant direction, changing speed (linear acceleration);
       2. constant speed, changing direction (centripetal acceleration);
       3. change in both speed and direction (angular acceleration).
http://www.physicsclassroom.com/mmedia/circmot/ucm.cfm
Quote
An object moving in a circle is accelerating. Accelerating objects are objects which are changing their velocity - either the speed (i.e., magnitude of the velocity vector) or the direction. An object undergoing uniform circular motion is moving with a constant speed. Nonetheless, it is accelerating due to its change in direction. The direction of the acceleration is inwards.
http://www.sparknotes.com/physics/dynamics/uniformcircularmotion/section1.rhtml
Quote
Because the direction of a particle moving in a circle changes at a constant rate, it must experience uniform acceleration.
http://web.utk.edu/~cnattras/Physics221Spring2013/modules/m5/uniform_circular_motion.htm
Quote
An object moving in a circle of radius r with constant speed v is accelerating.  The direction of its velocity vector is changing all the time, but the magnitude of the velocity vector stays constant.  The acceleration vector cannot have a component in the direction of the velocity vector, since such a component would cause a change in speed.  The acceleration vector must therefore be perpendicular to the velocity vector at any point on the circle.  This acceleration is called radial acceleration or centripetal acceleration, and it points towards the center of the circle.


Title: Re: Newton's Laws of Motion
Post by: DuckDodgers on May 30, 2014, 08:19:53 PM
Can you point to which of those links invalidate what I said?
Title: Re: Newton's Laws of Motion
Post by: Rama Set on May 30, 2014, 08:26:51 PM
Where did I say you said anything invalid?  I said garygreen elaborated on your statement. Think of it like an onion with many layers.

 The ISS does not have a constant speed anyway.  It requires periodic boosts in its speed to maintain its orbit, but it is rather close to constant, but a constant velocity does not mean no acceleration if that is what you are getting at.  Again, from garygreen's post:

http://www.gravity.phys.uwm.edu/~doqui/doqui/209-5.pdf
Quote
An object revolving in a circle is continuously accelerating even when the speed remains constant.
http://dev.physicslab.org/Document.aspx?doctype=3&filename=CircularMotion_CentripetalAcceleration.xml
Quote
An object is said to be moving in uniform circular motion when it maintains a constant speed while traveling in a circle. Remember that since acceleration is a vector quantity comprised of both magnitude and direction, objects can accelerate in any of these three ways:
 
       1. constant direction, changing speed (linear acceleration);
       2. constant speed, changing direction (centripetal acceleration);
       3. change in both speed and direction (angular acceleration).

Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 08:36:02 PM
When speaking of orbit, is a constant speed not a constant angular velocity?  You've really muddied up the whole discussion.
You might be making the mistake of assuming a perfectly circular, non-assisted, non-decaying orbit centered about perfect sphere. Neither is true of the ISS and the RE.

Also please verify for me: when you say "constant speed" you mean that the magnitude of linear velocity of the orbiting object is unvarying throughout its orbit, right?
Title: Re: Newton's Laws of Motion
Post by: Pete Svarrior on May 30, 2014, 08:44:50 PM
How does Thork claim that the ISS does not accelerate without his making a mistake? Are you saying that if I was merely confused about the importance of a 12% error, I did not make a mistake? Maybe you've confused his mistake of ignorance with my error of judgement.
For the record, I don't buy your "error of judgement" explanation. It's quite clear that you didn't realise the correct answer was 8.7m/s2 and went with standard g because you didn't think about it long enough. I do not suspect that you lacked the knowledge necessary to make the correct conclusion - hence it was a mistake. However, even if it was an error of judgement regarding whether or not an unacceptable error margin is acceptable, that's essentially the definition of a mistake (See: http://www.merriam-webster.com/dictionary/mistake).

Quote from: http://www.merriam-webster.com/dictionary/mistake
to blunder in the choice of <mistook her way in the dark>
[...]
a wrong judgment :  misunderstanding
[...]

A lack of knowledge is not a mistake. Therefore, while I still agree that Thork was very wrong, I disagree that he made a mistake.

You might find this explanation useful: http://www.physicsclassroom.com/Class/1DKin/U1L1b.cfm

The link you provided uses the terms "magnitude" and "value" interchangably. Since the question was "what's the value of the acceleration?" and not "what's the acceleration?", you have now single-handedly confirmed that the question was that of magnitude (and thus the direction was unnecessary).

Quote from: http://www.physicsclassroom.com/Class/1DKin/U1L1b.cfm
Scalars are quantities that are fully described by a magnitude (or numerical value) alone.

Of course, acceleration is a vector quantity. However, the value of acceleration is not one. Think velocity vs. speed.

Again, you really should quote directly, not add "context" yourself. I count that you dropped 32 characters. But, hey, it's not like accurate quoting is essential as long as you get the context right.
Unfortunately, this is impossible - I cannot fit an accurate quote of both the question and your untruncated answer within the character limit. Omitting the question would completely eliminate the context and make it unreadable to the viewers unless they explicitly followed the link in the quote. Those who have any doubts about the appropriateness of my quote can still click on "Quote from: Gulliver [...]" and read the messages in context. However, since the context was relayed accurately, and the only part of your message that got omitted is irrelevant (and could only make you look worse), this is overall a good deal for you.

Finally, together with BBCode, my sig is precisely 300 characters long. I already had to cheat the system a bit by neglecting to close some of the tags and relying on SMF to fill the gaps. A few (very few, and notably not enough to fulfill your request) characters could be saved if I got rid of line breaks. Feel free to count yourself!

Code: [Select]
To know that some RE'ers don't understand grade school physics look no further than:
[quote author=Gulliver link=topic=1577.msg30543#msg30543 date=1401389390]
[quote author=inquisitive]
What is the value of the acceleration? [i][of the ISS towards the Earth][/i]
[/quote]Approximately: 9.8 m/s[sup]2

That said, if you do come up with a refactoring of the quote that accurately portrays your mistake (that you believed the magnitude of the acceleration of the ISS was 9.8 m/s2) which I can fit in 300 characters together with "To know that some RE'ers don't understand grade school physics look no further than:" and which still links back to your original blunder, I'll consider using it.
Title: Re: Newton's Laws of Motion
Post by: DuckDodgers on May 30, 2014, 08:47:09 PM
Are you having trouble with understanding the definition of constant or speed?  Of course there is going to be variation, nothing can travel at the same speed without some variation, but it's speed is roughly constant when averaged.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 09:33:12 PM
A lack of knowledge is not a mistake. Therefore, while I still agree that Thork was very wrong, I disagree that he made a mistake.
So posting a conclusion with a lack of knowledge is not a blunder. So as long as I didn't know that the 8.7 m/s/s was a better answer, i did not make a mistake. I doubt that you'd agree with yourself. For example: pizzaplanet is a known child molester in his home country and will surely be put in jail. Even though I've made a claim without adequate knowledge to support it, I've not made a mistake right?
Quote
You might find this explanation useful: http://www.physicsclassroom.com/Class/1DKin/U1L1b.cfm

The link you provided uses the terms "magnitude" and "value" interchangably. Since the question was "what's the value of the acceleration?" and not "what's the acceleration?", you have now single-handedly confirmed that the question was that of magnitude (and thus the direction was unnecessary).

Quote from: http://www.physicsclassroom.com/Class/1DKin/U1L1b.cfm
Scalars are quantities that are fully described by a magnitude (or numerical value) alone.

Of course, acceleration is a vector quantity. However, the value of acceleration is not one. Think velocity vs. speed.
Please do quote where your read that "value" of a vector quantity is the same as the magnitude of a vector quantity. You've only quoted that magnitude is a numerical value. There's nothing in that quote that speaks to the value of a vector quantity. What is the value of pair [1,1]? What is the magnitude of the vector [1,1]?
Quote
v
Again, you really should quote directly, not add "context" yourself. I count that you dropped 32 characters. But, hey, it's not like accurate quoting is essential as long as you get the context right.
Unfortunately, this is impossible - I cannot fit an accurate quote of both the question and your untruncated answer within the character limit. Omitting the question would completely eliminate the context and make it unreadable to the viewers unless they explicitly followed the link in the quote. Those who have any doubts about the appropriateness of my quote can still click on "Quote from: Gulliver [...]" and read the messages in context. However, since the context was relayed accurately, and the only part of your message that got omitted is irrelevant (and could only make you look worse), this is overall a good deal for you.

Finally, together with BBCode, my sig is precisely 300 characters long. I already had to cheat the system a bit by neglecting to close some of the tags and relying on SMF to fill the gaps. A few (very few, and notably not enough to fulfill your request) characters could be saved if I got rid of line breaks. Feel free to count yourself!

Code: [Select]
To know that some RE'ers don't understand grade school physics look no further than:
[quote author=Gulliver link=topic=1577.msg30543#msg30543 date=1401389390]
[quote author=inquisitive]
What is the value of the acceleration? [i][of the ISS towards the Earth][/i]
[/quote]Approximately: 9.8 m/s[sup]2

That said, if you do come up with a refactoring of the quote that accurately portrays your mistake (that you believed the magnitude of the acceleration of the ISS was 9.8 m/s2) which I can fit in 300 characters together with "To know that some RE'ers don't understand grade school physics look no further than:" and which still links back to your original blunder, I'll consider using it.
I never believed that the magnitude of the acceleration was 9.8 m/s/s. You attack a straw man. Please note that you unfairly added the phrase "of the ISS towards the Earth" to inquistive's question. If you would be honest, you'd have more than enough characters.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 30, 2014, 09:35:06 PM
Are you having trouble with understanding the definition of constant or speed?  Of course there is going to be variation, nothing can travel at the same speed without some variation, but it's speed is roughly constant when averaged.
So its speed varies. Got it. Thork failed even with the switch to a new topic. Thanks for clearing that up for us.
Title: Re: Newton's Laws of Motion
Post by: juner on May 30, 2014, 09:40:50 PM
So posting a conclusion with a lack of knowledge is not a blunder.

PP didn't say it wasn't a "blunder."  He said it wasn't a mistake.  You should also go back and read the part about being intellectually dishonest.

Anyway, you lost that round.  I am sure you will make up for it.
Title: Re: Newton's Laws of Motion
Post by: markjo on May 31, 2014, 03:51:44 AM
Are you having trouble with understanding the definition of constant or speed?  Of course there is going to be variation, nothing can travel at the same speed without some variation, but it's speed is roughly constant when averaged.

Are you having trouble understanding that when an object is traveling at a constant speed while traveling in a circular path, then it is accelerating because acceleration is defined as the rate of change of velocity with velocity being defined as speed in a direction?  Since the direction that the ISS is traveling is constantly changing, therefore the velocity is changing, therefore the ISS is, indeed, accelerating.  It really isn't that difficult a concept to understand, unless you're Sceptimatic.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 31, 2014, 03:54:12 AM
Are you having trouble with understanding the definition of constant or speed?  Of course there is going to be variation, nothing can travel at the same speed without some variation, but it's speed is roughly constant when averaged.

Are you having trouble understanding that when an object is traveling at a constant speed while traveling in a circular path, then it is accelerating because acceleration is defined as the rate of change of velocity with velocity being defined as speed in a direction?  Since the direction that the ISS is traveling is constantly changing, therefore the velocity is changing, therefore the ISS is, indeed, accelerating.  It really isn't that difficult a concept to understand, unless you're Sceptimatic.
Well explained. DD, I hope you're reading these great posts. You can really learn something about grade school physics.
Title: Re: Newton's Laws of Motion
Post by: markjo on May 31, 2014, 04:38:02 AM
Are you having trouble with understanding the definition of constant or speed?  Of course there is going to be variation, nothing can travel at the same speed without some variation, but it's speed is roughly constant when averaged.

Are you having trouble understanding that when an object is traveling at a constant speed while traveling in a circular path, then it is accelerating because acceleration is defined as the rate of change of velocity with velocity being defined as speed in a direction?  Since the direction that the ISS is traveling is constantly changing, therefore the velocity is changing, therefore the ISS is, indeed, accelerating.  It really isn't that difficult a concept to understand, unless you're Sceptimatic.
Well explained. DD, I hope you're reading these great posts. You can really learn something about grade school physics.
BTW, this acceleration that the ISS is experiencing is known as centripetal acceleration (http://theory.uwinnipeg.ca/physics/circ/node6.html).
Title: Re: Newton's Laws of Motion
Post by: DuckDodgers on May 31, 2014, 02:20:41 PM
I can see why Thork dropped out of this conversation, you people just refuse to read the posts and assume they say something they don't.  Angular acceleration is what has been talked about this entire time.  Go back through and read the posts and you'll see that.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on May 31, 2014, 02:37:56 PM
I can see why Thork dropped out of this conversation, you people just refuse to read the posts and assume they say something they don't.  Angular acceleration is what has been talked about this entire time.  Go back through and read the posts and you'll see that.
Simply False. Read the link in my sig. Thork definitely said, and meant (linear) acceleration. Only dealing with linear acceleration would be an appropriate reply to my post, which he quoted. Go back and read what Thork was replying to. Even pp agrees that Thork is woefully wrong.
Title: Re: Newton's Laws of Motion
Post by: spaceman spiff on May 31, 2014, 02:57:39 PM
I can see why Thork dropped out of this conversation, you people just refuse to read the posts and assume they say something they don't.  Angular acceleration is what has been talked about this entire time.  Go back through and read the posts and you'll see that.
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The ISS doesn't accelerate. Its in low earth orbit at a constant speed of around 17000mph To have a force of acceleration in one direction and an opposing force that cancels that out in the opposite direction does not mean one is accelerating. If I get in my car and accelerate to 150mph before the wind resistance is so great my car stops accelerating doesn't mean I am still accelerating. It means I am now at 150mph and that is that as the forces balanced.
You are confusing angular velocity with angular acceleration.
https://en.wikipedia.org/wiki/Angular_velocity
He says VERY clearly that the ISS doesn't accelerate and that the forces on it are balanced. If he was talking about angular acceleration, he should have added the word angular, which he did not. Therefore it'safe to assume he was talking in the more general sense of acceleration.
Title: Re: Newton's Laws of Motion
Post by: Rama Set on May 31, 2014, 04:05:48 PM
I can see why Thork dropped out of this conversation, you people just refuse to read the posts and assume they say something they don't.  Angular acceleration is what has been talked about this entire time.  Go back through and read the posts and you'll see that.

Please feel free to drop out then. No harm, no foul.
Title: Re: Newton's Laws of Motion
Post by: spoon on June 01, 2014, 03:40:14 PM
Sure, the ISS isn't moving on a straight line. That's not exactly a groundbreaking realization. I really don't think Thork would argue that point. I just don't see why you would describe rotoational motion linearly.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on June 01, 2014, 04:54:26 PM
Sure, the ISS isn't moving on a straight line. That's not exactly a groundbreaking realization. I really don't think Thork would argue that point. I just don't see why you would describe rotoational motion linearly.
Yes, the ISS isn't moving in a straight line.

Yes, Thork explicitly argued that the ISS is moving in a straight line. To say that the ISS does not accelerate means that the ISS, if it moves, moves only in a straight line. Please see the various links for a grade school lesson on the meaning of acceleration.

You build a straw man, and an irrelevant one at that. No REer has suggested describing rotational motion as simple linear motion (I think that what you meant by "linearly".).
Title: Re: Newton's Laws of Motion
Post by: spoon on June 01, 2014, 06:07:01 PM
No REer has suggested describing rotational motion as simple linear motion (I think that what you meant by "linearly".).

Your whole schpiel has been that the ISS has linear acceleration relative to the earth. Do you mean to say that its motion relative to the earth isn't rotational?

Think hard about that. Your previous response indicates their is a severe gap in your critical thinking.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on June 01, 2014, 07:07:04 PM
No REer has suggested describing rotational motion as simple linear motion (I think that what you meant by "linearly".).

Your whole schpiel has been that the ISS has linear acceleration relative to the earth. Do you mean to say that its motion relative to the earth isn't rotational?

Think hard about that. Your previous response indicates their is a severe gap in your critical thinking.
No. The ISS rotates about the RE. Why do you ask? Do you think an object can't rotate about the RE and have linear acceleration?
Title: Re: Newton's Laws of Motion
Post by: spoon on June 01, 2014, 10:46:32 PM
No REer has suggested describing rotational motion as simple linear motion (I think that what you meant by "linearly".).

Your whole schpiel has been that the ISS has linear acceleration relative to the earth. Do you mean to say that its motion relative to the earth isn't rotational?

Think hard about that. Your previous response indicates their is a severe gap in your critical thinking.
No. The ISS rotates about the RE. Why do you ask? Do you think an object can't rotate about the RE and have linear acceleration?
ur dense
Title: Re: Newton's Laws of Motion
Post by: spaceman spiff on June 01, 2014, 10:57:19 PM
No REer has suggested describing rotational motion as simple linear motion (I think that what you meant by "linearly".).

Your whole schpiel has been that the ISS has linear acceleration relative to the earth. Do you mean to say that its motion relative to the earth isn't rotational?

Think hard about that. Your previous response indicates their is a severe gap in your critical thinking.
No. The ISS rotates about the RE. Why do you ask? Do you think an object can't rotate about the RE and have linear acceleration?
ur dense
Someone correct me if I'm wrong, but as far as I know linear acceleration is just the force divided by the mass, and it's the second derivative of the position vector w.r.t. time. Since there's only one force acting on the ISS and its velocity vector changes with time, it follows that it does have linear acceleration. The term linear has nothing to do with the movement, it's just to differentiate it from angular acceleration, which can be defined as the torque divided by the moment of inertia, or the derivative of the angular velocity w.r.t. time. Any object in uniform circular motion has a non-zero linear acceleration and zero angular acceleration.
Title: Re: Newton's Laws of Motion
Post by: spoon on June 01, 2014, 11:06:16 PM
No REer has suggested describing rotational motion as simple linear motion (I think that what you meant by "linearly".).

Your whole schpiel has been that the ISS has linear acceleration relative to the earth. Do you mean to say that its motion relative to the earth isn't rotational?

Think hard about that. Your previous response indicates their is a severe gap in your critical thinking.
No. The ISS rotates about the RE. Why do you ask? Do you think an object can't rotate about the RE and have linear acceleration?
ur dense
Someone correct me if I'm wrong, but as far as I know linear acceleration is just the force divided by the mass, and it's the second derivative of the position vector w.r.t. time. Since there's only one force acting on the ISS and its velocity vector changes with time, it follows that it does have linear acceleration. The term linear has nothing to do with the movement, it's just to differentiate it from angular acceleration, which can be defined as the torque divided by the moment of inertia, or the derivative of the angular velocity w.r.t. time. Any object in uniform circular motion has a non-zero linear acceleration and zero angular acceleration.

Mostly irrelevant. I'd say about 85%.

However, the bit in bold is important because that approximates the motion of the ISS.

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The term linear has nothing to do with the movement
This part is just wrong.
Title: Re: Newton's Laws of Motion
Post by: markjo on June 02, 2014, 12:17:47 AM
No REer has suggested describing rotational motion as simple linear motion (I think that what you meant by "linearly".).

Your whole schpiel has been that the ISS has linear acceleration relative to the earth. Do you mean to say that its motion relative to the earth isn't rotational?

Think hard about that. Your previous response indicates their is a severe gap in your critical thinking.
Yes, the circular orbit of the ISS has a (more or less) constant angular velocity, but it also experiences centripetal acceleration.  Why is that so hard to understand?  ???
Title: Re: Newton's Laws of Motion
Post by: Gulliver on June 02, 2014, 12:36:34 AM
No REer has suggested describing rotational motion as simple linear motion (I think that what you meant by "linearly".).

Your whole schpiel has been that the ISS has linear acceleration relative to the earth. Do you mean to say that its motion relative to the earth isn't rotational?

Think hard about that. Your previous response indicates their is a severe gap in your critical thinking.
No. The ISS rotates about the RE. Why do you ask? Do you think an object can't rotate about the RE and have linear acceleration?
ur dense
Someone correct me if I'm wrong, but as far as I know linear acceleration is just the force divided by the mass, and it's the second derivative of the position vector w.r.t. time. Since there's only one force acting on the ISS and its velocity vector changes with time, it follows that it does have linear acceleration. The term linear has nothing to do with the movement, it's just to differentiate it from angular acceleration, which can be defined as the torque divided by the moment of inertia, or the derivative of the angular velocity w.r.t. time. Any object in uniform circular motion has a non-zero linear acceleration and zero angular acceleration.
Did you maybe forget that the object in a perfectly circular orbit is still accelerating, at a right angle to its instantaneous velocity, toward the center of the orbit? If it weren't, it would fly off (standard pedantic disclaimer on FoRs) and not be in orbit any longer.
Title: Re: Newton's Laws of Motion
Post by: spaceman spiff on June 02, 2014, 01:23:03 AM
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The term linear has nothing to do with the movement
This part is just wrong.
This whole discussion is basically a discussion on semantics but you're wrong. In usual terminology, linear acceleration is any change in velocity, which is a vectorial quantity. Therefore, any rotational movement will have linear acceleration.
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Did you maybe forget that the object in a perfectly circular orbit is still accelerating, at a right angle to its instantaneous velocity, toward the center of the orbit? If it weren't, it would fly off (standard pedantic disclaimer on FoRs) and not be in orbit any longer.
No, and that's why I said that any object in uniform circular motion will have a non zero linear acceleration.
Title: Re: Newton's Laws of Motion
Post by: Gulliver on June 02, 2014, 03:04:08 AM
Quote
Quote
The term linear has nothing to do with the movement
This part is just wrong.
This whole discussion is basically a discussion on semantics but you're wrong. In usual terminology, linear acceleration is any change in velocity, which is a vectorial quantity. Therefore, any rotational movement will have linear acceleration.
Quote
Did you maybe forget that the object in a perfectly circular orbit is still accelerating, at a right angle to its instantaneous velocity, toward the center of the orbit? If it weren't, it would fly off (standard pedantic disclaimer on FoRs) and not be in orbit any longer.
No, and that's why I said that any object in uniform circular motion will have a non zero linear acceleration.
Sorry, I erred. Please ignore that post.