Question

A father and son pushed their car to bring it to the side of a road as it had stalled in the middle of the road. They experienced that they had to push with all their might initially to move the car. But the push required to keep the car rolling was smaller. Explain.

Answer 1

The push required to move the car initially is same as static friction.

The push required to keep it rolling is same as rolling friction.

Since rolling friction is less than static friction, initial push was of higher force than the later push.

Answer 2

overcome the frictional force force needed is f=ma