Where does Newton's third law fail?

[LCSphysicist]

Homework Statement

.

Relevant Equations

Fab = minus Fba

I have read in some books and articles of classic mechanics that the Newton's third law does not always hold, could you say an example to me?

 

[jbriggs444]

Homework Statement:: .
Relevant Equations:: Fab = minus Fba

I have read in some books and articles of classic mechanics that the Newton's third law does not always hold, could you say an example to me?

You will need to provide proper references to these books and articles before we can discuss them.

 

[LCSphysicist]

You will need to provide proper references to these books and articles before we can discuss them.

Moyses

You are not obliged to understand portuguese, but in the last paragraph:
"We will see later that, to non contact forces, the third law can cease to count"He goes on, and say that despite this, the momentum conservation conveniently generalized always is validI just want to know more about "We will see later that, to non contact forces, the third law can cease to worth"

 

[LCSphysicist]

Moyses Nussenveig is the author of "Fisica Basica", in Brazil we only say Moyses to refer to his books.

 

[Delta2]

In Classical Newtonian Mechanics Newton's 3rd law is one of the axioms so it does always hold.

In Quantum Mechanics it is not an axiom, neither it can be deduced from the other axioms of quantum mechanics. I guess there are some physical phenomena that involve violation of Newton's 3rd law and can be explained by quantum mechanics but not by classical Newtonian mechanics.

 

[Delta2]

Moyses Nussenvoig is the author of "Basic Physics", in Brazil we only say Moyses to refer to his books.

Does this book have chapters on quantum physics/quantum mechanics or is it only about classical physics?

 

[LCSphysicist]

Does this book have chapters on quantum physics/quantum mechanics or is it only about classical physics?

There is four books, the first is classical physics. The last book is quantum mechanics.
So, it makes sense what you said, the later that he said is, actually, really laaaaatttttterrrr hah

 

[etotheipi]

Google translated version:

Spoiler: Translated Version

...it means that the horse's traction force is transmitted to the stone by the rope, without changing.
This result is characteristic of a "weightless" wire or rope, and has already been tacitly admitted to discussion of Ex. 3.

So far we are only dealing with the dynamics of a particle (cf. p. 64), so that in the examples above, we treat each body as if it were a particle. In this treatment, it is not well defined at which point of each body the different forces are applied considered (because we are treating bodies as if they have negligible dimensions). Later, when we discuss particle systems, we will see that, with regard to the movement of a body as a whole, it is permissible to consider that the resulting force to which it it is subject if it is applied at a point, which is called the "center of mass" of that body.

It is interesting to note the role of friction furnaces in example 6. What would happen if the horse was on the road and the stone on a frozen lake? And if the situation invert? What if they were both on the surface of a frozen lake? It would be possible to displacement of the horse and stone forward in the absence of friction?

We arrived at Newton's 3rd law from the moment conservation principle, for the
special case of contact forces (p. 76). We will see later that, for forces that are not of contact, the 3. law may no longer apply. On the other hand, the principle of conservation of the moment, conveniently generalized, it always remains valid. This is why we prefer...

 

[jbriggs444]

I just want to know more about "We will see later that, to non contact forces, the third law can cease to count"

Thank you for the reference. There is room for some discussion here. Though possibly outside the context of the homework forum.

I suspect that the author is considering problems with a finite maximum speed (the speed of light limit) when two bodies interact at a distance. If the two bodies interact instantly, that breaks the speed limit. If they do not interact instantly then you have a force over here without an immediate third law partner force over there.

One resolution to this is through the concept of "fields". Each body interacts locally with the field. The field carries momentum. You never have two bodies interacting directly with forces at a distance.

 

[wrobel]

Thank you for the reference. There is room for some discussion here. Though possibly outside the context of the homework forum.

I suspect that the author is considering problems with a finite maximum speed (the speed of light limit) when two bodies interact at a distance. If the two bodies interact instantly, that breaks the speed limit. If they do not interact instantly then you have a force over here without an immediate third law partner force over there.

One resolution to this is through the concept of "fields". Each body interacts locally with the field. The field carries momentum. You never have two bodies interacting directly with forces at a distance.

I think that before saying that the 3 Newton law fails, a conscientious specialist should describe which exactly model he is speaking about. Moreover it is assumed by default that if somebody refers the 3 Newton law then the Newton mechanics is under consideration. I think this guy just attempts to draw attention to himself
by cheap tricks