speed of the ball

Question

A machine throws tennis balls contains a spring with a spring constant of 145N/m. When you push a ball into the machine,the spring compresses by 1.5cm.The mass of the ball is 55g 

Calculate the speed of the ball as it leaves the machine when you fire it.

Answer 1

Set the potential energy of the compressed spring equal to the kinetic energy of the ball, and solve for the speed.

 

kx²/2 = mv²/2

 

v = x√(k/m)

 

x = 0.015 m

k = 145 N/m

m = 0.055 kg

 

Plug in these numbers and get v in m/s.