Newton’s Third Law of Motion

Definition:

“To every action there is an equal and opposite reaction.”

OR

“When two bodies exert mutual forces on one another, the two forces are always equal in magnitude and opposite in direction.”

Mathematically we can write;

FAB = – FBA

it is important to remember that the action and reaction forces always act on the same body there would be no net force on that body and no accelerated motion.

Examples:

1. When a bat strikes a ball, the bat exert a force on the ball (The action)

 

Explanation:

Forces come in pairs. We find by experiment that when one body exerts a force on a second body the second body always exerts a force on the first. Further more, we find these forces always to be equal in magnitude but opposite in direction.

Newton's third law

Let a body A exert a force FAB on body B, then the body B exerts the force FBA. These forces having the same magnitude but opposite is direction

FAB = – FBA

It is important to remember that the action and reaction forces always act on different bodies. If they acted on the same body there would be not net force on that body and no accelerated motion.

Examples:

1. when a bat strikes a ball the bat exert a force on the ball (the action) and the ball exerts an equal and opposite force on the bat.

2. when you kick a football, the forward force your foot exerts on the ball launches it into its trajectory, but you also feel the force the ball exerts on the ball your foot.

 

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