Chapter 8, Problem 17Q

To determine

The reason why most moving or rotating objects eventually slow down and stop

Answer to Problem 17Q

Solution:

When there is no outside force acting on the object, its momentum will be conserved. The motion of the moving objects is opposed by the air resistance and friction which are the outside forces. Because of this, the moving object will slow down and then it will stop.

Explanation of Solution

Most moving or rotating objects slow down and stop because of the presence of frictional forces. These small forces are generally ignored in case of mathematical calculations and net force or net torque is assumed to be zero. In such a case, our assumption of conservation of momentum or angular momentum holds true.