A child does 5.0 J of work on a spring while loading a ball into a spring-loaded toy gun. If mechanical energy is conserved, what will be the kinetic energy of the ball when it leaves the gun?

A 0 J

B 3.7 J

C 2.5 J

D 5.0 J

Option D is the correct answer.

Explanation:

Here mechanical energy is conserved.

Kinetic energy + Potential energy = Constant.

First the child does 5.0 J of work on a spring while loading a ball into a spring-loaded toy gun.

That is potential energy = 5 J

Kinetic energy = 0 J

Kinetic energy + Potential energy = 0 + 5 = 5 J

Secondly the spring is released.

That is potential energy = 0 J

Kinetic energy = ?

Kinetic energy + Potential energy = Constant = 5 J

Kinetic energy + 0 = 5 J

Kinetic energy is 5 J

Option D is the correct answer.