Chapter 4.3, Problem 29PP

To determine

To identify: The force acting on the freely falling brick.

The force applied by the brick on other object.

Answer to Problem 29PP

The gravitational force is acting on the brick applied by the earth.

The brick also applies the gravitational force on the earth.

Explanation of Solution

Introduction:

The gravitational force is a attractive because it always pulls the masses together. The magnitude of gravitational force is directly related to the product of masses $m_1$ and $m_2$ and also inversely related to the distance between them.

  $F=\frac{G{m}_1{m}_2}{R^2}$

When objects falls on the earth surface from some height then gravitational force applied by the earth acts on it.

  $\begin{array}{l}F=\frac{G{M}_e{m}_b}{R^2}\\ \text{where,}\\ F=\text{ force}\\ M_e=\text{Mass of earth}\\ m_b=\text{mass of brick}\\ R=\text{distnace between the brick and center of earth}\end{array}$

The direction of gravitational force is towards the center of earth. Therefore, brick falls on the surface of earth.

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

The free body diagram is shown as,

  

Conclusion:

The gravitational force applied by the earth is acting on freely falling object.

The brick also exert the same amount of gravitational force on Earth.