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Inertial reference frames

by eprparadox
Tags: inertial, reference frames
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eprparadox
#1
Aug11-10, 05:21 PM
P: 81
1. The problem statement, all variables and given/known data
An example of an inertial reference frame is:
A. any reference frame that is not accelerating
B. a frame attached to a particle on which there are no forces
C. any reference frame that is at rest
D. a reference frame attached to the center of the universe
E. a reference frame attached to Earth


2. Relevant equations



3. The attempt at a solution

This isn't really a homework problem because the answer is given to me as B. I guess that makes sense. If there are no forces on an object, then it will move with constant velocity and thus, must be an inertial reference frame.

But I'm not clear as to why the answer can't be A or C. Is it because the idea of a frame of reference is relative and the ideas of "at rest" and "not accelerating" aren't defined within a given frame of reference?

I think I'm confused on this whole idea of inertial reference frames. If anyone has some insight that can help me, that would be great. Thanks a lot.
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution
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diazona
#2
Aug11-10, 06:59 PM
HW Helper
P: 2,155
Quote Quote by eprparadox View Post
This isn't really a homework problem because the answer is given to me as B. I guess that makes sense. If there are no forces on an object, then it will move with constant velocity and thus, must be an inertial reference frame.

But I'm not clear as to why the answer can't be A or C. Is it because the idea of a frame of reference is relative and the ideas of "at rest" and "not accelerating" aren't defined within a given frame of reference?
That's the only reasoning I can think of by which you can conclude that answers A and C are incorrect but that B is. The idea would be that all motion is relative, so "at rest" and "not accelerating" would have to be defined with respect to some other reference frame. If the other reference frame is non-inertial, then being at rest (or being "not accelerating") with respect to that reference frame also puts you in a non-inertial frame.

Honestly, I think this is a badly written question, and it's more likely to just confuse you than to test your understanding of anything.

For future reference, by the way, the standard definition of an inertial reference frame is one in which the law of inertia applies: an object subject to no external forces moves with a constant velocity. As far as anyone knows, this is equivalent to saying that an inertial reference frame is one in which Newton's second law (ΣF=ma) holds.
eprparadox
#3
Aug11-10, 07:44 PM
P: 81
Hey thanks a lot for the quick response. I appreciate it.


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