Inertial reference frames problem

AI Thread Summary
An inertial reference frame is defined as one where an object subject to no external forces moves with constant velocity, making option B the correct answer. The confusion arises because options A and C imply conditions that are relative and depend on other frames of reference, which may not be inertial themselves. The discussion highlights that terms like "at rest" and "not accelerating" lack universal definitions without a specified reference frame. The question is criticized for being poorly constructed, as it may confuse rather than clarify the concept of inertial frames. Understanding that an inertial frame adheres to Newton's laws is essential for grasping the concept.
eprparadox
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Homework Statement


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


Homework Equations





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.

 
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eprparadox said:
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.
 
Hey thanks a lot for the quick response. I appreciate it.
 
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