Question

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.

(a) 25J

(b) 12.5J

(c) 0

(d) 30J

The question was asked in an internship interview.

This intriguing question comes from First Law of Thermodynamics topic in chapter Thermodynamics of Physics – Class 11

Answer 1

Right option is (b) 12.5J

The best explanation: 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.