Actually,everything is inter connected and it is logical to think that something has to be first and others are mere consequences of it.
Pre-requisite knowledge:
What the source says:
the conservation laws were much more fundamental than Newton's Third Law. The sources suggest that the action-reaction pairs are necessary for momentum to be conserved, so they are a consequence of the conservation of momentum.
How I understand that statement of the source:
You want to say that conservation of momentum is more basic than the concept of newtons third law.
My response to the statement:
I could,as well, say that 'conservation of momentum' is necessary for action-reaction pairs to exist
How all of this seems to me:
It's like the good-old: which came first,chicken or egg question?
My opinion:
What I'd like to say:
Since our concept of force has been derived from the concept of momentum I'd like to conclude that the concept of 'momentum' is more fundamental than that of 'force'.
How to intuitively understand what I just said:
- Assume that the concept of momentum doesn't exist:
What is force then?
- Assume that the concept of force doesn't exist:
what is momentum then?
well,I can still answer this question without having to know what force is.But, in the former case we couldn't answer what force is without having to know what momentum is.
But,which is a consequence of which : 'third law' is of 'conservation of momentum' or viceversa?
Does this statement:
well,I can still answer this question without having to know what force is.But, in the former case we couldn't answer what force is without having to know what momentum is.
imply that 'third law' is a consequence of'conservation of momentum'?
consider the following examples:
Consider a single body of mass m moving in vacuum with a speed v.This body
has mometum(P=mv).
Does the law of conservation of momentum hold true?
Yes,ofcourse because the momentum of a body remains constant.
where is newtons third law now?
Let's say that you are observing a head-on elastic collision between two bodies,happening in vacuum.In this case momentum is conserved.The third law works.
Before collision we don't see any contact forces,so we don't know if newtons third law works or not,but there is a net momentum for the system and it is conserved.
During collision we know that newtons third law works and the system still has
momentum conserved.
Now how can you to decide whether 'conservation of momentum' arose because 'newtons
third law works or to 'conserve momentum' newtons third law works?
My answer:
In example 1 we saw that momentum is conserved for the body and we don't see any forces.
In example 2: Imagine that you are testing the so called law of conservation of momentum.You observed that the bodies changed velocities after collision.you are trying to explain why that has happened because newtons first law says that a body cannot change its state of motion without the action of force.So you came up with the concept of contact forces and these forces follow the third law.
you also observed that net momentum of the system is same before and after collision
you want to know if the forces arose so as to conserve momentum or because the forces
arose, momentum is conserved?
That's the: which came first,chicken or egg question?
why don't you think that these two concepts are two fundamental laws of nature?
i.e it's a property that when the two bodies interact,collide,there are equal and
opposite forces and momentum is conserved before and after collision.
In our system of two bodies we observe that momentum is a property of a system and
forces are interactions between two bodies of a system.
Conclusion:
Conservation of momentum is a property of the system and 'newtons third law'is a concept which describes the interaction between particles/systems.
You need one to explain the other in our case and most of the other cases too,both are interrelated.
you can use the concept of momentum to explain newtons third law and you can,also,use the concept of newtons third law and obtain the law of conservation of momentum
To put it simply:
we used the concept of momentum to understand force.After we understood it quite well we observed that when two bodies interact,like collision,there are two laws called'newtons third law' and 'conservation of momentum'.
Both,the egg and the chicken came first and last,as well.
NOTE:
I have given some bold statements in my answer.please correct me if you think that I am wrong anywhere