Question

If a baseball is traveling 30 m/s towards a batter who then hits it in the opposite direction at 45 m/s and the ball was in contact with the bat for 0.1 seconds then what is the acceleration of the baseball?

Answer 1

In 0.1 seconds ball changed its velocity from 30 m/s to -45 m/s (sign '-' because the direction is opposite). By definition, its acceleration is:

$$a = \dfrac{-45m/s-30m/s}{0.1s} = -750 m/s^2$$

Answer. 750 m/s^2 in the direction opposite to the initial movement.