Physics Help? C4:6

Question

A person exerts an upward force of 60 N to hold a backpack.   This is the “action” force.

 

6)         a)          Describe the magnitude and direction of the “reaction” force.  Be specific.

b)         Upon what object does the reaction force act?  Be specific.

c)          What object exerts the reaction force?  Be specific. 

Answer 1

(6a)

Step 1 :

A person exerts a action force of 60 N on backpack.

Newton's third law :

According to Newton's third law, for every action force there is an equal (in size) and opposite (in direction) reaction force. Forces always come in pairs - known as "action-reaction force pairs."

Consider an example hitting a baseball. The bat exerts a force on the ball. This is the action force. The ball exerts and equal and opposite force on the bat. This is the reaction force.

The two forces in a pair act on different objects and are equal in strength and opposite in direction.

The force of A on B is equal in magnitude and opposite in direction of the force of B on A:

F(A on B) = - F(B on A)

Therefore the backpack exerts a action force of on a person and opposite direction with respect to action force.

Solution :

The backpack exerts a action force of on a person and opposite direction with respect to action force.

Answer 2

(6b)

Newton's third law :

Every action force there is an equal (in size) and opposite (in direction) reaction force on any object.

There are some cases in which reaction force can not be exerted.

Consider an example of if a football is kicked from both sides at the same time, it doesn't go anywhere, because the two feet kicking it exert equal and opposite forces on the same ball and cancel each other out.

However, when you kick a football with just one foot, that foot exerts an action force on the ball, and at the same time, the ball exerts a reaction force on your foot. In this case, the forces don't cancel out, so the ball travels through the air.

Therefore every object exerts the reaction force.

Answer 3

(6c)

Newton's third law :

Every action force there is an equal (in size) and opposite (in direction) reaction force on any object.

There are some cases in which reaction force can not be exerted.

Consider an example of if a football is kicked from both sides at the same time, it doesn't go anywhere, because the two feet kicking it exert equal and opposite forces on the same ball and cancel each other out.

However, when you kick a football with just one foot, that foot exerts an action force on the ball, and at the same time, the ball exerts a reaction force on your foot. In this case, the forces don't cancel out, so the ball travels through the air.

Therefore every object exerts the reaction force.