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. 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 × "mass" × ("velocity")^2`

= `1/2 × 0.5 × (2)^2`

= `1/2 × 0.5 × 2 × 2`

= 1J

Hence, potential energy of compressed spring = 1.0 J.