Chapter 4.3, Problem 31PP

To determine

To identify: The force acting on the ball.

The force exerted by the ball.

The Free body diagram of ball.

Answer to Problem 31PP

The gravitational force is acting on the ball and it is applied by the earth.

The ball exerts a force on the earth.

Explanation of Solution

Introduction:

The gravitational force is always attractive in nature because it always pulls two or more masses together.

The magnitude of gravitational force between two object is directly related to the product of their masses $m_1$ and $m_2$ and also inversely related to the distance between them.

  $F=\frac{G{m}_1{m}_2}{R^2}$

The directional of gravitational force is towards the center of mass of other object.

When ball is tossed then the direction of initialvelocity is in upward direction. And only gravitational force acts in downward direction.

In free body diagram, only those forces are drawn which are acting on the ball. The free body diagram is shown as,

  

Where,

  $\begin{array}{l}{F}_e=\text{Force applied by earth on ball}\\ F_m=\text{Force applied by ball on earth}\end{array}$

From the free body diagram, ball is also applying force on the earth.

According to Newton’s third law of motion, the ball will also exerts the same amount of gravitational force on earth.

Thus, $F_e=F_m$

Conclusion:

The gravitational force is acting on the ball.

Ball also applying the gravitational force on earth.