Laws of Motion
3.0 Newton's third law of motion
3.0 Newton's third law of motion
To every action, there is always an equal and opposite reaction.
Examples,
1. Book kept on a table
A book lying on a table applies a force on the table. It is equal to the weight of the book $(W)$. This is the force of action.
The table supports the book by applying an equal Normal force $(N)$ on the book. This is the force of reaction.
Note: Action reaction pairs are equal in magnitude and opposite in direction.
2. Walking
While walking a person presses the ground in the backward direction (action) by his foot.
The ground pushes the person in forward direction with an equal force (reaction).
The component of reaction in the horizontal direction helps the person to move forward.
3. Swimming
A swimmer pushes the water backward (action), therefore the water pushes the swimmer forward (reaction) with same force. Hence the swimmer swims.
