Consider the situation of the previous question from a frame moving with a speed v 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?
(i) In this condition, the let’s consider the velocity of the ball to be 
and the velocity of the frame to be
.
Relative velocity of the object w.r.t to the frame
Initial kinetic energy of the object
final kinetic energy of the object
(ii) Work done by the kinetic friction= final kinetic energy – Initial kinetic energy
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