Question

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

Answer 1

Given, mass of the bolt is 0.3 kg , speed of the elevator is 7 m/s and the length of the elevator is 3 m .

Potential energy E is given as,

E=mgh

Here, m is the mass of the bolt, h is the length of the elevator.

Substitute the values in above expression.

E=0.3×9.8×3 =8.82 J

The relative velocity of the bolt in respect with lift is 0 , hence total potential energy is converted into heat energy. Thus

Heat energy produced=8.82 J

As there is no relative velocity between lift and bolt, hence there will be no change in heat produced and will remain same.