Re: Newton's Laws of Motion
« Reply #40 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
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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
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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.
« Last Edit: May 26, 2014, 12:17:10 AM by garygreen »
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Thork

Re: Newton's Laws of Motion
« Reply #41 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
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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.


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.

Re: Newton's Laws of Motion
« Reply #42 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.


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)
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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
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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?
« Last Edit: May 26, 2014, 02:11:18 AM by garygreen »
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Offline Gulliver

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Re: Newton's Laws of Motion
« Reply #43 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.
Don't rely on FEers for history or physics.
[Hampton] never did [go to prison] and was never found guilty of libel.
The ISS doesn't accelerate.

Re: Newton's Laws of Motion
« Reply #44 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.



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.
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Offline jroa

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Re: Newton's Laws of Motion
« Reply #45 on: May 29, 2014, 12:11:58 PM »
The ISS goes at a constant speed.  Look it up.

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Offline markjo

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Re: Newton's Laws of Motion
« Reply #46 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.
Abandon hope all ye who press enter here.

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Offline Gulliver

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Re: Newton's Laws of Motion
« Reply #47 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".)
Don't rely on FEers for history or physics.
[Hampton] never did [go to prison] and was never found guilty of libel.
The ISS doesn't accelerate.

Re: Newton's Laws of Motion
« Reply #48 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?

Offline Gulliver

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Re: Newton's Laws of Motion
« Reply #49 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
Don't rely on FEers for history or physics.
[Hampton] never did [go to prison] and was never found guilty of libel.
The ISS doesn't accelerate.

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Offline Pete Svarrior

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Re: Newton's Laws of Motion
« Reply #50 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 suggests something more akin to 8.7m/s2.
« Last Edit: May 29, 2014, 07:27:52 PM by pizaaplanet »
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Offline Pete Svarrior

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Re: Newton's Laws of Motion
« Reply #51 on: May 29, 2014, 07:23:48 PM »
For a more detailed explanation:



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



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
« Last Edit: May 29, 2014, 07:45:31 PM by pizaaplanet »
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Offline spoon

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Re: Newton's Laws of Motion
« Reply #52 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.
inb4 Blanko spoons a literally pizza

Thork

Re: Newton's Laws of Motion
« Reply #53 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. :-(

Offline Gulliver

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Re: Newton's Laws of Motion
« Reply #54 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 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.
« Last Edit: May 29, 2014, 10:19:55 PM by Gulliver »
Don't rely on FEers for history or physics.
[Hampton] never did [go to prison] and was never found guilty of libel.
The ISS doesn't accelerate.

Re: Newton's Laws of Motion
« Reply #55 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
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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
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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
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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
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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
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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.

« Last Edit: May 29, 2014, 10:09:12 PM by garygreen »
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Offline spoon

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Re: Newton's Laws of Motion
« Reply #56 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.
inb4 Blanko spoons a literally pizza

Offline Gulliver

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Re: Newton's Laws of Motion
« Reply #57 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.
Don't rely on FEers for history or physics.
[Hampton] never did [go to prison] and was never found guilty of libel.
The ISS doesn't accelerate.

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Offline Pete Svarrior

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Re: Newton's Laws of Motion
« Reply #58 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 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.
« Last Edit: May 30, 2014, 02:19:03 AM by pizaaplanet »
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Offline Gulliver

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Re: Newton's Laws of Motion
« Reply #59 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 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.
« Last Edit: May 30, 2014, 02:56:13 AM by Gulliver »
Don't rely on FEers for history or physics.
[Hampton] never did [go to prison] and was never found guilty of libel.
The ISS doesn't accelerate.