Question

A current of 80 A flows for 1 hr, in a resistance across which there is a voltage of 2V. Determine the velocity with which a weight of 1 tonne must move in order that its kinetic energy shall be equal to the energy dissipated in the resistance.

Answer 1

Energy dissipated in the resistance 

= V It = 2 × 80 × 3600 = 576,000 J 

A weight of one tonne represents a mass of one tonne i.e., 1000 kg. Its kinetic energy is 

= (1/2) × 1000 × v² = 500 v² 

∴ 500 v² = 576,000 

∴ v = 1152 m/s.