Question

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

Answer 1

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.