4. A slingshot is used to fire a paper ball which has a mass of 0.04kg.
The elastic cord of the sling shot has a spring constant of 6N/m and is extended 40cm.
a) Calculate the elastic potential energy of the sling shot. (3)
b) Calculate the speed of the paper ball when it is fired. (3)
Assume no energy is dissipated when the paper ball is fired.