Newton Third Law of Motion The Action and Reaction Pair - Detailed Guide

In this article we discuss about, definition of Newton's third law of motion, Newton 's law of motion with examples in day to day life, Newton third’s law of motion solutions, action and reaction pairs with examples and solutions.

Define third law of motion/ Newton’s third law of motion/ third law of motion definition

Newton’s third law of motion define as law of action and reaction. Law of action and reaction states that, for every action, there will be an equal and opposite reaction.

In this universe, when any force is applied on an object, that object will exert an equal amount of force but in the opposite direction to that applied force. A force is nothing but an action of pull or pushes that acts on an object by which it causes an interaction with another object.

Force between objects can be classified as

• Contact force
• Action at a distance

Contact force happens when the two objects are having physical contact with each other. Examples of contact force are frictional force, air resistance, and tensional force.

Action at a distance force happens when the two objects do not have any physical contact with each other. Examples of action at a distance force are gravitational force, electrical force and magnetic force. When we jump on the ground even though your foot doesn’t touch the ground some gravitational force will appear on your feet by moving back to the ground.

Also read -

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Action and reaction pair in Newton’s 3rd law

According to Newton’s third law there will be an equal and opposite reaction for any action. Consider an object A and object B interact with each other, by Newton’s third law these objects will exert force on one another.

This can be given with a mathematical expression as

F_a= - F_b

Here when object A exerts a force on another object B, then an equal amount of force will be exerted back on object A but in the opposite direction which is denoted with a minus (-) symbol.

Now we can illustrate the Action and reaction pair with an example.

• When we sit on a chair, you will exert a downward force on the chair which is action. Similarly the chair will exert an upward force on you which is a reaction. These two forces are action and reaction pairs. So a pair of forces acts on objects which are interacting with each other.
• When a fish swims in water it exerts a downward force on the water – action. Since the force occurs in mutual interaction the water will exert an equal amount of force to the fish but in the opposite direction i.e upwards – reaction.
• Consider a bird flying in the sky. The bird swings the wing in downward direction to push the air downwards - action. Since the force occurs in mutual interaction the air will exert an equal amount of force on the wing but in the opposite direction i.e upwards- reaction.

Images of Newton's 3rd law of motion

Here the trampoline jumping trick shows Newton's third law of motion- action reaction pairs.

NCERT Physics Notes:

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Action – the jumper jumps on trampoline, he exerts the force on trampoline

Reaction – the trampoline pushes the jumper up, the trampoline exerts the same force on the jumper making him move upwards.

Day to day life examples with solution using Newton’s third law of motion/ third law of motion examples with solutions

• When you jump on the ground, you exert some force on the ground which is the action. Similarly the ground exerts the same force on us so you move up which is a reaction.
• Propulsion of rocket – when the engineers design the rocket they use Newton’s third law of motion. The fuel when ignited the gas rushes from the rocket- action. This gas exerts a push action on the ground. In turn the ground exerts an upward force on the rocket-reaction. The rocket moves upwards and the speed increases.
• When a person swims in a pool, that person pushes the water downwards which in turn the water pushes the person upwards.
• Aeroplanes and birds flying in the air are Newton's 3rd law of motion example.
• Consider a car moving on the road speeding up. For doing this, the car wants to exert a force on the road, or else your car does not accelerate. Similarly the road will also exert an equal force on the car but the force will be in the opposite direction.

Law of action and reaction examples in sports

• In football, when the player kicks the football. The player exerts a force to kick the ball – action, so the same amount of force in the opposite direction is exerted on the player foot by the ball – reaction.
• When we hit the tennis ball using a racket. The more force you apply on the racket to hit the ball – action, the same amount of force in the opposite direction will be exerted to your hand by the racket – reaction.
• In swimming, the more the force you extend on the wall to push to water – action ,similarly the same amount of force in the opposite direction the wall extends on you it moves – reaction.
  Also read :

• NCERT notes Class 11 Physics Chapter 5 Laws of Motion
• NCERT solutions for Class 11 Physics Chapter 5 Laws of Motion
• NCERT Exemplar Class 11 Physics Solutions Chapter 5 Laws of Motion

Examples of Newton's third law of motion/ Newton's third law of motion examples/ newton's third law examples/ third law of motion examples

Third law of motion examples in daily life is given below.

• Gun mechanism
• Bouncing a ball
• Walking on ground
• Using of hammer for hammering
• Balloon air is evacuating
• Rowing a boat
• Moving of car
• Sports like hockey
• Using an elastic band
• Slingshot

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• NCERT Exemplar Class 11th Physics Solutions
• NCERT Exemplar Class 12th Physics Solutions
• NCERT Exemplar Solutions for All Subjects