Question

Suppose that a 20 kg ball rolling at 1 m/s collides with another static ball (also 20 kg). The collision causes the rolling ball to come to rest in 2 ms. What was the average force applied to the static ball during the collision?

Answer 1

We know, by Newton's second law, that the force is given by:

`F=ma`

since we don't know the acceleration of the ball we can't calculate the force yet. What we know is that the rolling ball comes to rest in 2 ms. Then the acceleration is:

`a=(0-1)/(2*10^(-3))=-500`

In here the minus sign indicates that the acceleration is going againts the motion, that is, it is stopping the ball.

Now that we know this we can calculate the force on the rolling ball:

`F=(20)(-500)=-10000`

Now, from Newton's third law, we know that the force on the static ball is equal in magnitude but opposite in direction, therefore the force on it is 10,000 N