Question

What is the change of momentum of a ball weighing a mass 0.2kg rolls with a velocity of 2.0 m/s and rebounds back at 2.0m/s

Answer 1

We can find the change of momentum of a ball from the definition of the momentum:

$$\Delta p=m\Delta v=m(v_f-v_i),$$ $$\Delta p=0.2\ kg\cdot(-2.0\ \dfrac{m}{s}-2.0\ \dfrac{m}{s})=-0.8\ \dfrac{kgm}{s}.$$

The sign minus means that the change of momentum of the ball is directed away from the wall.

Answer:

$\Delta p=0.8\ \dfrac{kgm}{s},$ away from the wall.