# Can every mass obey the Newton's 3rd law?

As in, if we were able to produce a very huge amount of force on a very small body, would it push back with the same force? Given it doesn't break or disintegrate. Like if we electromagnetically put tremendous force on a single electron, would it push back with the same force when released?

• Commented May 21, 2019 at 12:25

Yes, a very small body can exert a very large force if it is being acted upon by a very large force (and vice-versa). There is no limit in terms of the mass of the objects involved as to whether they follow the third law of Newton or not. For example, I would like to point out an example which is trivial but is similar in an emotional sense to what you have in mind: an apple exerts the same force on the Earth as the entire Earth does on the apple. More dramatically speaking, for an apple lying on the ground, you can say that the Earth is supported by the apple just as much as you can say that the apple is supported by the Earth.

Now, there are violations of the third law of Newton but those are related to fields carrying the momentum on their own--not related to how massive the particles are (or not).

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Commented May 21, 2019 at 13:01
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Newton's third law doesn't tell anything about mass. It is about forces, and it says in fact that momentum is conserved in every interaction. See Compton scattering, where a photon interacts electromagnetically with an electron and then it scatters.

Newton's third law isn't a law about massive objects. The law is about forces. Newton's third law essentially just tells us that all forces are interactions. It doesn't tell us anything about the dynamics resulting from such interactions.

Like if we electromagnetically put tremendous force on a single electron, would it push back with the same force when released?

If your single electron is experiencing a force then this force is due to an interaction between the electron and whatever the other thing (things) is that is causing the interaction. I am confused by your "when released" part. Whatever is pushing on the electron will also experience a force of the same magnitude in the opposite direction. once force stops the interaction stops.

• That was just because of the thought process being a steady increase of the force on the electron rather than a sudden increase. And then making one side of the force zero so as to "release" it. As in, why can't we use such a mechanism is space? Commented May 21, 2019 at 13:13

## Rule:

All mass follows Newton's 3rd law, no exceptions.(reason,to conserve momentum)

"electromagnetically put tremendous force on a single electron" -When force is exerted on a electron, the instrument forcing the electron will also experience a resistive force itself.(force due to Lenz's law) So, yeah, 3rd law stays conserved here.

## Example:

You use a magnet to pull a iron rod, the iron rod will also pulls the magnet towards it. Replace iron rod by electron and the magnet by some field source(eg charged body) and similar effect will happen.

• So do you want to say that linear momentum conservation is more fundamental than 3rd law?? Commented May 21, 2019 at 14:16
• Yes. Conservation of momentum is more fundamental. Commented May 22, 2019 at 0:38
• So,3rd law is not a law but a theorem!Isn't it? Commented May 22, 2019 at 2:52
• The Third law is not a theorem. Theorem: It is derived mathematically from axioms(Axioms are statements assumed to be true). Laws: They can not be derived. In physics the natural laws are actually axioms(assumed to be true as it is always followed in nature, eg conservation laws). Commented May 22, 2019 at 12:02