In a Little League baseball game, the 145 g ball enters the strike zone with a speed of 15.0 m/s. The batter hits the ball, and it leaves his bat with a speed of 21.0 m/s in exactly the opposite direction. What is the magnitude of the impulse delivered by the bat to the ball?

5.22 Ns

Explanation:

A consequence of Newton's second law of motion is that:

Impulse = change in momentum

The initial momentum = (0.145 kg) * (15.0 m/s)

The final momentum = (0.145 kg) * (-21.0 m/s)

The final momentum has a negative sign because the ball returned in an opposite direction.

Change in momentum = final momentum - initial momentum = (0.145 kg) * (-21.0 m/s) - (0.145 kg) * (15.0 m/s)

= - 0.145 (21.0 + 15.0) kg m/s

= - 0.145 * 36.0 kg m/s

= - 5.22 kg m/s

The magnitude of the impulse is thus 5.22 Ns.