Action and reaction are equal and opposite,but why dont they cancell ?

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Discussion Overview

The discussion revolves around the concept of Newton's third law of motion, specifically addressing why action and reaction forces do not cancel each other out in certain scenarios. Participants explore the implications of these forces in different contexts, including dynamics and force balance.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why action and reaction forces do not cancel out in the same way as forces acting on a body from opposite directions.
  • Another participant asserts that action and reaction forces do cancel when considering the net contribution to linear momentum across both objects involved in the interaction.
  • A different viewpoint emphasizes that while action and reaction forces are equal and opposite, they act on different objects, which is why they do not cancel for a single object.
  • One participant clarifies that when analyzing forces on an object, only the forces acting on that object are included, not the forces it exerts on others.

Areas of Agreement / Disagreement

Participants express differing views on the cancellation of action and reaction forces, with some asserting they do cancel in a broader context, while others maintain that they do not cancel for individual objects. The discussion remains unresolved regarding the implications of these forces in specific scenarios.

Contextual Notes

Participants highlight the importance of considering the dynamics of the situation and the specific objects involved when discussing action and reaction forces. There is an implicit assumption that the context of the forces matters significantly in their analysis.

tushar
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Action and reaction are equal and opposite,but why don't they cancell ?...

Unlike other forces, like for example.. it a body is pressed from top and below with a same force.. the body stays there and its said that the forces cancell out.. why not here ?
 
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They do cancel. The net contribution to linear momentum (totalled over both objects) from a third law force pair is zero.

They don't cancel on a single object because only one of the two forces acts on that object.
 
The action is the force which you apply.

The reaction is the force which is applied on you.

So they cancel as a pair, but you must work out the dynamics by considering action-reaction separately ... like when a ball strikes a wall, or two balls collide.
 
The third law says that the force you exert on an object is equal in magnitude and opposite In direction to the force that the object exerts on you. But, if you are doing a force balance on the object , you include only forces acting on the object, and not forces acting on you.

Chet
 

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