Yes, the rest frame of Ball 2 is such a frame of reference (surprise!), but it is not inertial and therefore not necessarily a good choice to describe the process.feynman1 said:Is there any sort of reference frame in which Ball 2 is always fixed (at rest) so that one can look at their relative velocity always in that reference frame?
Do you mean it's not inertial at the instant of the collision but inertial before and after? If so, Ball 2 won't be fixed in that frame, which isn't what I look for.DrStupid said:Yes, the rest frame of Ball 2 is such a frame of reference (surprise!), but it is not inertial and therefore not necessarily a good choice to describe the process.
Relative velocity is per definition the velocity of ball A in the rest frame of ball B (or vice versa). But if the relative velocity doesn't change, then there is not much of a collision.feynman1 said:2 balls (Ball 1 and Ball 2) collide fully elastically and their relative velocity stays the same as that before the collision. Is there any sort of reference frame in which Ball 2 is always fixed (at rest) so that one can look at their relative velocity always in that reference frame? Here 'always' includes before and after the collision.
It is not inertial at the instant of the collision because Ball 2 (which is accelerated during the collision) is fixed in that frame.feynman1 said:Do you mean it's not inertial at the instant of the collision but inertial before and after? If so, Ball 2 won't be fixed in that frame, which isn't what I look for.
Just edited the original question, relative v changes sign.A.T. said:Relative velocity is per definition the velocity of ball A in the rest frame of ball B (or vice versa). But if the relative velocity doesn't change, then there is not much of a collision.
Right, then have you an answer to the original question?DrStupid said:It is not inertial at the instant of the collision because Ball 2 (which is accelerated during the collision) is fixed in that frame.
He already answered it in post 2!feynman1 said:Right, then have you an answer to the original question?
I knew all along that such a frame written in post 2 doesn't work well. Then can we conclude that there's no inertial reference frame in which Ball 2 is always fixed?Dale said:He already answered it in post 2!
Yes.feynman1 said:Then can we conclude that there's no inertial reference frame in which Ball 2 is always fixed?
A reference frame in collision problems is a coordinate system used to measure the position and motion of objects involved in a collision. It serves as a point of reference to analyze the movement and interactions of the objects.
The choice of reference frame affects the measurements and calculations made in a collision problem. Choosing the right reference frame can simplify the problem and make it easier to understand and solve.
In a collision, the initial and final velocities of objects can be determined by measuring their positions at different times in the chosen reference frame. The change in position over time can be used to calculate the velocities using the equations of motion.
Yes, different reference frames can give different results in a collision problem. This is because the motion of an object can appear different depending on the observer's point of view. It is important to use a consistent reference frame throughout the problem to avoid confusion and errors.
The most appropriate reference frame in a collision problem is one that simplifies the problem and makes it easier to analyze and solve. It should also be chosen based on the type of collision and the motion of the objects involved. In some cases, choosing a reference frame in which one of the objects is at rest can make the problem easier to solve.