Chapter 7, Problem 42A

Suppose you exert 200 N on your refrigerator and push it across the kitchen floor at constant velocity. What friction force acts between the refrigerator and the floor? Is the friction force equal and opposite to your 200-N push? Does the friction force make up the reaction force to your push?

To determine

The friction force between the refrigerator and the floor.

To identify: Whether the friction force equal and opposite to the $200\text{N}$ push. Also, whether the friction force makes up the reaction force to the push.

Answer to Problem 42A

The friction force acts between the refrigerator and floor is $-200\text{ N}$ .

The friction force equal and opposite to the $200\text{N}$ push.

The friction force does not make up the reaction force to the push.

Explanation of Solution

Given:

Force exerted on refrigerator is 20 N.

Formula used:

The frictional force which is acting in between any of the two surfaces will depends on the type of material with which it is in contact.

The expression for friction force is

  $f=\mu N$

Here, $\mu$ is the coefficient of friction and $N$ is the normal force.

Calculation:

The net force acting on the block is zero due to the constant velocity. So the friction force acting on the floor is equal and opposite to the force exerted on the system.

Hence, the friction force that is acting between the refrigerator and floor will be $-200\text{ N}$ .

The reaction force is the force applied by the body on an object. Hence, the friction force will not exert the reaction force. Also, the friction force does not make up the reaction force to the push.

Conclusion:

Thus, the friction force acts between the refrigerator and floor is $-200\text{ N}$ .

Thus, the friction force equal and opposite to the $200\text{N}$ push.

Thus, the friction force does not make up the reaction force to the push.