A 100 kg block is started with a speed of `2.0 m s^(-1)` on a long, rough belt kept fixed in a horizontal position. The coefficient of kinetic friction between the block and the belt is 0.20. (a) calculate the change in the internal energy of the block=-belt system as the block comes to a stop on the belt. (b) consider the sutuation from a frame of reference moving at `2.0 m s^(-1)` along the initial velocity of the block. as seen from this frame, the block is gently put on a moving belt and in due time the block starts moving with the belt at `2.0 m s^(-1)`, calculate the increase in the kinetic energy of the block as it stops slipping past the belt. (c ) find the work done in this frame by the external force holding the belt.