Question

if action is equal and opposite to reaction then why action is not cancelled reaction

Answer 1

Action is equal and opposite to reaction.

They are the pair of the forces which acts on two different bodies.

They never act on same body only their line of action are same.

And we know that to cancel forces it should be acting on the same body at the same point.

Also it's called action not reaction because it's not the after effect of any action. It's the cause of the reaction on the second body.

Action and reaction forces are pair of cause and effect on pair of bodies. One acts as cause (source) for other and other acts as the effect of the first.

Hence if we apply some force on one body and we are getting an equal and opposite effect on the other then the first force is obviously a source and cause and will be called as action and the second will the effect or the reaction and they won't cancel as they are acting on two different bodies at the same time.

Example : Jumping from a boat

Here the jumper is causing action by jump and the reaction we can see on the boat as it moves back.

Answer 2

Equal and Opposite but Not Balanced

Balanced forces are equal and opposite forces that act on the same object. That's why they cancel out. Action-reaction forces are equal and opposite forces that act on different objects, so they don't cancel out. In fact, they often result in motion