A 6.8-kg ball rolling at 2.2m/s bumps into a pillow and stops in 0.50s.

1. Find the force exerted by the pillow.

2. How much force does the ball exert on the pillow?

Question

A 6.8-kg ball rolling at 2.2m/s bumps into a pillow and stops in 0.50s.

1. Find the force exerted by the pillow.

2. How much force does the ball exert on the pillow?

ybarrap · Answer

1. The ball decelerates from 2.2 m/s to zero in 0.50 s, so its rate of acceleration is a=-2.2/0.5 m/s^2 = -4.4 m/s^2. The force required to stop the ball is F=ma, where m = 6.8 kg and a = -4.4 m/s^2. The negative means that the ball is pushing in the negative x direction. Use SI units in your calculations, therefore use 6.8, not 6,800.

2. For every action there is an equal an opposite reaction. Therefore, the ball exerts the exact same force as the pillow, but in the opposite direction (i.e. the positive x direction)