(II) A train is moving along a track with constant speed υ1 relative to the ground. A person on the train holds a ball of mass m and throws it toward the front of the train with a speed υ2 relative to the train. Calculate the change in kinetic energy of the ball (a) in the Earth frame of reference, and (b) in the train frame of reference. (c) Relative to each frame of reference, how much work was done on the ball? (d) Explain why the results in part (b) are not the same for the two frames–after all, it’s the same ball.
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