To study the Newton's third law of motion using two spring balance, we need to understand the concept of Newton's third law of motion.

• Two spring balances


• A stand


• A hook


• A weight

1. Hang one spring balance from the stand using the hook.


2. Hang the second spring balance from the first spring balance using the hook.


3. Add a weight to the second spring balance.


4. Observe the reading on the first spring balance.


5. Observe the reading on the second spring balance.


6. Record the readings in a table.


7. Repeat the experiment with different weights.

To study the Third Law of Motion using two spring balances.
# The Theory
Newton’s Third Law of Motion states: ‘To every action there is an equal and opposite reaction’.
It must be remembered that action and reaction always act The Third Law of Motion indicates that when one object exerts a force on another object, the second object instantaneously exerts a force back on the first object. These two forces are always equal in magnitude, but opposite in direction.
These forces act on different objects and so they do not cancel each other. Thus, Newton’s Third Law of Motion describes the relationship between the forces of interaction between two objects.
Whenever two bodies interact with each other, the force exerted by the first body on the second is called action. The force exerted by the second body on the first body is called reaction. The action and reaction are equal and opposite.
For example, when we placed a wooden block on the ground, this block exerts a force equal to its

weight, W = mg

acting downwards to the ground. This is the action force. The ground exerts an equal and.

opposite force W’ = mg


on the block in the upward direction. This is the reaction force.