I'm confused about how Newton's 3rd law applies to friction. If you slid an object across a table then the particles you are sliding against would exert the same force back, but wouldn`t this mean constant velocity since the object has equal acceleration in opposite directions, but it isnt really a force to begin with since if its sliding by itself then you are no longer exerting a force, the only force is the force of friction?

Please help, keep in mind Im new to physics and I only know the basics of newtonian laws.

  • 1
    $\begingroup$ Can you make your question a bit more clear? $\endgroup$
    – Normie
    Dec 16 '15 at 7:53
  • $\begingroup$ Things accelerate because of the second and third law, since if one object exerts a force on another object that same force will be exerted on the object, a force means acceleration, which depends on the mass of the object. Im basically asking what will happen when an object accelerated by 5 newtons, exerts this force on another object. $\endgroup$
    – Ben
    Dec 16 '15 at 8:16
  • $\begingroup$ @Avik is right the question needs to be more clear. You are totally jumbling the concepts and your question needs to be revised. $\endgroup$ Dec 16 '15 at 11:47

The friction on the sliding object and the corresponding friction because of Newton's 3rd law are two equal but opposite forces that do not both work on the object.

Only one of them works on the object itself, which therefore accelerates (decelerates). The other one works on the ground - that is, on the Earth.

If an astronaut pushes another astronaut in outer space, then this other astronaut will feel the force an start accelerating. The first astronaut will feel an equal force backwards from Newton's 3rd law and will accelerate. These two forces apply on two different objects, not in the same object.


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