Newton's Third Law
Category : JEE Main & Advanced
To every action, there is always an equal (in magnitude) and opposite (in direction) reaction.
(1) When a body exerts a force on any other body, the second body also exerts an equal and opposite force on the first.
(2) Forces in nature always occurs in pairs. A single isolated force is not possible.
(3) Any agent, applying a force also experiences a force of equal magnitude but in opposite direction. The force applied by the agent is called 'Action' and the counter force experienced by it is called 'Reaction'.
(4) Action and reaction never act on the same body. If it were so, the total force on a body would have always been zero i.e. the body will always remain in equilibrium.
(5) If \[{{\overrightarrow{F}}_{AB}}\]= force exerted on body A by body B (Action) and \[{{\overrightarrow{F}}_{BA}}\]= force exerted on body B by body A (Reaction)
Then according to Newton?s third law of motion \[{{\overrightarrow{F}}_{AB}}=-{{\overrightarrow{F}}_{BA}}\]
(6) Example : (i) A book lying on a table exerts a force on the table which is equal to the weight of the book. This is the force of action.
The table supports the book, by exerting an equal force on the book. This is the force of reaction.
As the system is at rest, net force on it is zero. Therefore force of action and reaction must be equal and opposite.
(ii) Swimming is possible due to third law of motion.
(iii) When a gun is fired, the bullet moves forward (action). The gun recoils backward (reaction)
(iv) Rebounding of rubber ball takes place due to third law of motion.
(v) While walking a person presses the ground in the backward direction (action) by his feet. The ground pushes the person in forward direction with an equal force (reaction). The component of reaction in horizontal direction makes the person move forward.
(vi) It is difficult to walk on sand or ice.
(vii) Driving a nail into a wooden block without holding the block is difficult.
You need to login to perform this action.
You will be redirected in
3 sec
