A block of mass 1kg is given a velocity of 5m/s on a horizontal flat surface. What will be the change in internal energy of the block-surface system, when the block comes to rest. The coefficient of kinetic friction is 0.3 and coefficient of static friction is 0.4.

Correct Answer: 12.5J
The kinetic energy of the block will change into internal energy of the system. Initial kinetic energy = 0.5*1*25 = 12.5J. Therefore the internal energy change = 12.5J.