A child bounces a 48 g superball on the side- walk. The velocity change of the superball is from 25 m/s downward to 14 m/s upward.

A child bounces a 48 g superball on the side-walk. The velocity change of the superball isfrom 25 m/s downward to 14 m/s upward.If the contact time with the sidewalk is1800s, what is the magnitude of the average forceexerted on the superball by the sidewalk?