Chapter 3, Problem 29A

When a ball rolls down an inclined plane, it gains speed because of gravity. When rolling up it loses speed because of gravity. Why doesn’t gravity play a role when it rolls on a horizontal surface?

To determine

To Explain:Gravity doesn’t play a role when a ball rolls on a horizontal surface.

Answer to Problem 29A

There is no role of gravity as no work is done.

Explanation of Solution

Introduction:

In the case of an inclined plane, a ball rolling down the plane gains speed because of gravity but while rolling up, it loses its speed due to gravity.

In the case of a horizontal surface, the force of weight will be perpendicular to the displacement of the ball. The work done is given by:

  $W=Fd\cos \theta$

Since, $\theta ={90}^0$

So, work done against gravity is zero. Hence, there is no role of gravity.

Conclusion:

Thus, there is no role of gravity as no work is done.