Question

A player hits a ball of mass 0.3kg which was moving eastwards with a velocity of 10m/s causing it now to move with a velocity of 15m/s westwards. The forces of the blow acts on for 0.01s . Calculate the average force exerted on the ball by the player.

Answer 1

Let's choose eastwards as a positive direction. Then the change of the velocity was the following:

$$\Delta v = 15m/s -(-10m/s) = 25m/s$$

Accroding to the second Newton's law, the average force is:

$$F_{av} = m\dfrac{\Delta v}{\Delta t}$$

where $\Delta t = 0.01s$ is the time the force acted on the ball, and $m=0.3kg$ is its mass. Thus, obtain:

$$F_{av} = 0.3kg\cdot \dfrac{25m/s}{0.01s} = 750 N$$

Answer. 750 N.