Is Newton's 3rd law incorrect?

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1. Sep 22, 2015

is the concept hypthetical

2. Sep 22, 2015

Abullais Ghazi

No it's not incorrect...It is applicable for macroscopic bodies but not applicable for microscopic bodies.

3. Sep 22, 2015

DEvens

Microscopic as well.
https://en.wikipedia.org/wiki/Atomic_recoil

4. Sep 23, 2015

Suraj Powar

To every actions there's equal and opposite reaction is not hypothetical.
It is true for microscopic and macroscopic bodies as the sizes of forces acting on bodies are acting equally.
But we can't say that the reaction is instantaneous as when a chemical reaction takes place the reaction doesn't take place in seconds it does take time.

5. Sep 23, 2015

DEvens

Chemical reactions are not what is being referred to in Newton's third law.

6. Sep 23, 2015

Staff: Mentor

No. But why are you thinking it might be?

7. Sep 25, 2015

Karan Punjabi

Newton's third law work for every object microscopic as well as macroscopic. And it is instantaneous just think about the fact that when someone shoots a bullet from the rifle or any gun the recoils occur at that moment only and it occurs in the opposite direction of bullet fired

8. Sep 25, 2015

lightarrow

It can't be instantaneous in the sense that c is the limiting speed of interactions.

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lightarrow

9. Sep 25, 2015

Karan Punjabi

Albert Einstein proved through mathematical equations that the carriers which carry the information of gravity calles gravitons work at the speed of light so gravity works as fast as light

10. Sep 25, 2015

HallsofIvy

Staff Emeritus
So what is your point? What does the transfer of the reaction from one part of the gun to another or to your shoulder have to do with Newton's third law?

11. Sep 25, 2015

willem2

Both forces can still be the same and in opposite directions at the same time, because both forces will be delayed by the same amount.

12. Sep 25, 2015

Staff: Mentor

Consider two equal positive charges q1 and q2. q1 is traveling along the x-axis in the +x direction, and and q2 is at rest on the +y-axis, a distance y away from the origin. Calculate the Lorentz forces $\vec F_1 = q_1 (\vec E_2 + \vec v_1 \times \vec B_2)$ and $\vec F_2 = q_2 (\vec E_1 + \vec v_2 \times \vec B_1)$ at the moment that q1 passes through the origin. Are those two forces equal in magnitude and opposite in direction?

13. Oct 6, 2015

if i give a 10 newton force to an object say a steel scrap then the force will transfer automatically to sound energy,heat energy etcetc and during this time there will be a loss in energy which in return may give 9.5 or 9.8 or so but it cant give exact or equal to 10 newton.....

14. Oct 6, 2015

DrStupid

It can if the interaction is locally only. Of course this requires a much more general concept of "body".

15. Oct 6, 2015

lightarrow

Can you expand a bit?

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lightarrow

16. Oct 6, 2015

nasu

This description is flawed. You don't "give" a force and then receive another one back.
The force is a measure of interaction between two objects. If there is an interaction between you and another object, you and the object simultaneously act with a force of 10N on each other. If there are other forces acting at the same time, they are part of other 3rd law pairs. They can decrease the energy of the system, maybe.

17. Oct 6, 2015

DrStupid

The interaction between two distant charged particles can't be instantaneous but the local interaction between the particles and their electromagnetic field is instantaneous. Newton's third law applies to this situation if photons or even virtual photons are considered to be "bodies".

18. Oct 6, 2015

Staff: Mentor

This is not related to Newton's 3rd law. Newton's third law says that the force you exert on the steel scrap is the same as the force that the steel scrap exerts back on you.

19. Oct 6, 2015

Staff: Mentor

To amplify even a bit more: you don't "give" a force and then receive another one back because that implies that they are separate events. They aren't. The application of/exchange of forces is a single event.

20. Oct 7, 2015

lightarrow

It seems very very "stretched" to me, considered that many physicists consider virtual photons as nothing else than a mathematical "trick".

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lightarrow