AN INSIGHT INTO THE NEWTON'S THIRD LAW OF MOTION
STATEMENT OF NEWTON'S THIRD LAW OF MOTION
WHAT WE ASSUME:-
Every force has an equal and opposite reaction.
WHAT IT ACTUALLY IS:-
What we have learnt since younger times is incomplete information. That's why many of us are not able to solve many problems which are based on this conceptual law.
What we assume creates an image in our mind as a "cause and effect" theory which is absolutely correct and goes as follows-
However, this statement is a partial explanation of what's really going on. We can't apply the above logic in all situations.
So, what is the correct statement?
The correct statement is that - "Forces exist in pairs. These forces don't act on the same object in any case."
This last line is the most important fact which one must know regarding this law. To illustrate this we take an example of a simple block of mass "M" kg kept on a flat surface. In the free- body diagram of the block we see that two forces act on the body, which is the force "Mg" and the normal reaction "N"
We assume that the normal reaction and mg are action-reaction pairs, but this is not true at all.
If we consider that "mg" is the action force, then the reaction force will act on the "cause" of this force, which is the earth, as the gravity force acts in pairs.
So, the force "mg" also acts on the earth due to the block which is the reaction force. However, we don't see the effect of this force because acceleration a ∝ 1/M. Now, earth has a higher mass so its acceleration is very less, which we don't see.
Now, the normal reaction is a contact force (we already know that). Now, because the block has a tendency to move downwards because of the force of "mg" acting on the block. This block exerts a force "N1" on the floor. As a reaction force, the floor exerts a normal reaction "N" shown in the figure.
That's all for today!!
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