A bob of mass 0.3 kg falls from the ceiling of an elevator moving down with a uniform speed of `7ms^(-1)`. If hits the floor of the elevator (length of the elevator `=` 3m) and does not rebound. What is the heat produced by the impact ? Would your answer be different if the elevator were stationary ?

Explanation

P.E of bolt= mgh = `0.3 xx 9.8 xx 3 xx 8.82 J`
The bolt does not rebound. So the whole of the energy is converted into heat. Since the value of the acceleration due to gravity is the same in all inertial system, therefore the answer will not change even if the elevator is stationary.