[DuckDodgers]

Can you point to which of those links invalidate what I said?

[Rama Set]

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

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

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).

[Gulliver]

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?

[Pete Svarrior]

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).

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).

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.

[DuckDodgers]

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.

[Gulliver]

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?

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).

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]?

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.

[Gulliver]

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.

[juner]

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.

[markjo]

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.

[Gulliver]

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.

[markjo]

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.

[DuckDodgers]

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.

[Gulliver]

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.

[spaceman spiff]

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.

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.

[Rama Set]

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.

[spoon]

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.

[Gulliver]

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".).

[spoon]

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.

[Gulliver]

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?

[spoon]

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