Question

State and explain the law of action and reaction. by giving two examples. 

Answer 1

Law of action and reaction: In an interaction of two bodies A and B, the magnitude of action, i.e. the force F_AB applied by the body B on the body A, is equal in magnitude to the reaction, i.e., the force F_BA applied by the body A on the body B, but they are in directions opposite to each other.

 

Examples:

(i) When a book is placed on a table, it does not move downwards. It implies that the resultant force on the book is zero, which is possible only if the table exerts an upward force of reaction on the book, equal to the weight of the book.

(ii) While moving on the ground, we exert a force by our feet to push the ground backwards; the ground exerts a force of the same magnitude on our feet forward, which makes it easier for us to move.

 

Explanation: In the above stated example, there are two objects and two forces. In the first example, the weight of the book acts downwards (action) and the force of the table acts upwards (reaction).

In the second example, our feet exerts a force on the ground (action) and the ground exerts an equal and opposite force (reaction) on our feet.