This question is typical on some driver’s license exams: a car moving at 49 km/h skids 13 m with locked brakes. how far will the car skid with locked brakes at 122.5 km/h? assume that energy loss is due only to sliding friction. answer in units of m.

The croquet ball velocity v will be 56/500 the tennis ball velocity V after the impulse.

The second law (force = mass*acceleration) says that the same force will accelerate the balls by the inverse of their mass. That is, the force will continuously change the momentum:

f = 500a = 56A

Therefore a = f/500 and A = f/56

and a/A = 56/500.

The croquet ball will accelerate less, for whatever time or distance you apply the force.

The third law: for every action, there is an equal and opposite reaction. So, if in fact you apply the same force to strike each ball, you will feel the same reaction. That’s probably easier to do for a quick strike (the impulse case above) than for a long, smooth acceleration over distance, because the balls have very different elastic response. The body can tell how equally you applied force!

Explanation: