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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?
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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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