If I punch a wall with a force of certain magnitude (Example: 25N), I hurt myself. Does the wall return my fist, with a force higher than 25 N?

  • $\begingroup$ No. It doesn't. You exert a force on the wall and the wall exerts a reaction force on you. You get hurt because of the force the wall exerts on you. $\endgroup$
    – user139621
    Sep 9, 2017 at 18:40

1 Answer 1


The answer to your question is No.

Newton's third law states that action and reaction occur in pairs. But it is always a misconception that both of them act on the same body. By that logic if a force and an opposite force is acting on the same body, then the body should never move or precisely the body can never accelerate.

The correct explanation is that action and reaction occur on two separate bodies and their magnitude is equal. If you punch a wall with 25N, then you are applying a force on the wall. The wall in return exerts a force of 25 N on your fist, that is why you get hurt.

Another example can be that Earth is pulling the moon with a force F, and the moon is pulling the earth with a force of same magnitude F. But these two forces are being acted on two different bodies and both of them are being attracted towards each other. But since the mass of the Earth is greater than the mass of the moon the acceleration produced by that force on earth is little as compared to the acceleration produced by the force which earth acts on the moon. Hence the moon revolves around the earth and not the other way around.

  • $\begingroup$ Thanks For the explanation!!! Now I will try to to make my teacher reasoning Because this happen: In classic mechanic the force that return to me is 25N But in Relative mechanic, the force that returno to me is less than 25N $\endgroup$ Sep 9, 2017 at 18:53
  • $\begingroup$ Actually, the earth and moon both orbit a common barycenter that is located about 1,700 km below the Earth's surface, or 4,671 km off the Earth's center. $\endgroup$
    – BillDOe
    Sep 9, 2017 at 18:58
  • $\begingroup$ That is correct. But that is not what I am trying to say. I am saying that acceleration produced by earth on moon is greater than the acceleration produced by moon on earth even if the forces being acted on both of them are equal. $\endgroup$
    – Khushal
    Sep 10, 2017 at 5:23

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