Newton’s 3rd law of motion explains the quantitatively that how forces affect motion.But question is that where these forces come from?We noticed during observations that a force on any object always exerted by another object.
A horse pulls a cart ,a person walks on the ground, hammer pushes a nail,magnets attract paper clip.In all these examples a force exerted on one object and that force is exerted by another object.
But isaac newton realized that things are not from one sided.It is true because in the example of hammer and nail ,hammer exerts force on nail,but the nail exerts a force back on the hammer as well,due to this the speed of hammer rapidly reduced to zero.Only a strong force can reduce the speed of hammer,thus newton said that the two objects must be treated on an equal bases,such as the hammer exerts a force on nail and nail exerts a force back on hammer.This is the cause or essence of newton’s 3rd law of motion.
Newton’s Third law of motion definition
Newton’s 3rd law of motion deals with the reaction of a body when a force acts on it.Let a body A exerts a force on another body B ,the body B reacts against this force and exerts a force on body A.The force exerted by body A on B is the action force whereas the force exerted by body B on A is called the reaction force.Newton’s 3rd law of motion states that:
“To every action there is always an equal but opposite reaction.”
According to this law,action is always accompanied by a reaction force and the two forces must always be equal and opposite.Note that action and reaction forces act on different bodies.
Newton’s 3rd law of motion tells us four characteristics about forces.
- Forces always occur in pairs (action and reaction forces).
- Action and reaction are equal in magnitude.
- Action and reaction are opposite in direction.
- Action and reaction are act on different bodies.
Examples of newton’s 3rd law
- A book lying on a table
The weight of the books is acting on the table in the downward direction.This is the action,The reaction of the table acts on the books in the upward direction.
- Motion of air filled balloon
Take an air filled balloon is set free,the air inside it rushes out and the balloon moves forward.In this example,the action is by the balloon that pushes the air out of it when set free.The reaction of the air which escapes out from the balloon acts on the balloon forward.A rocket moves on the same principle.When its fuel burns,hot gases escape out from its tail with a very high speed.The reaction of these gases on the rocket causes it to move opposite to the gases rushing out of its tail.
- Flight of rocket
When fuel of rocket is burnt,hot gases rush out with great speed from tail of rocket.Due to reaction of these gases rockets move forward in the upward direction.
Watch video about this law of motion.