Question

A spring is kept compressed by a small trolley of mass 0.5 kg lying on a smooth horizontal surface as shown in the adjacent fig. 2.14 when the trolley is released, it is found to move at a speed v = 2 m s^-1. What potential energy did the spring possess when compressed?

Answer 1

Mass of trolley = 0.5 kg

Velocity = 2 m/s

When the compressed spring is released, its potential energy is converted into kinetic energy completely.

Potential energy of compressed spring = kinetic energy of moving trolley

Kinetic energy of trolley = 1/2 x mass x (velocity)² 

= 1/2 ×0.5 ×(2)² 

= 1/2 ×0.5 ×2×2=1J

Hence, potential energy of compressed spring = 1.0J