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Question
Consider the situation of the previous question from a frame moving with a speed v0 parallel to the initial velocity of the block. (a) What are the initial and final kinetic energies? (b) What is the work done by the kinetic friction?
Solution
The relative velocity of the ball w.r.t. the moving frame is given by \[v_r = v - v_0\]
(a) Initial kinetic energy of the ball =\[\frac{1}{2}m {v_r}^2 = \frac{1}{2}m(v - v_0 )^2\]
Also, final kinetic energy of the ball =\[\frac{1}{2}m(0 - v_0 )^2 = \frac{1}{2}m {v_0}^2\]
(b) Work done by the kinetic friction = final kinetic energy - initial kinetic energy
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