- #1
lonelywizard
- 3
- 0
Can someone help me to prove the law of conservation of momentum using an example?
Proving the Law of Conservation of Momentum: An Example
- Thread starter lonelywizard
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Homework Help Overview
The discussion revolves around proving the law of conservation of momentum, with participants exploring various examples and theoretical underpinnings in the context of physics.
Discussion Character
- Exploratory, Conceptual clarification, Assumption checking
Approaches and Questions Raised
- Participants suggest using practical examples such as car accidents or rockets to illustrate the law. There is debate about the definition of force and its implications for momentum conservation. Some express uncertainty about the foundational premises of Newton's laws and question their validity.
Discussion Status
The discussion is active, with participants questioning the nature of proof versus demonstration. There are multiple interpretations of how to approach the concept, and while some guidance is offered regarding definitions, no consensus has been reached on a definitive proof.
Contextual Notes
Participants note the challenge of proving concepts that are foundational in physics, such as Newton's first law, and the implications this has for understanding momentum conservation.
- #2
QuantumCrash
- 135
- 0
Hmm... right now I can't really think of any that actually PROVES it. But I can prove that it always works no matter what situation it is applied to. Just show a situation, e.g. car accidents, rockets, springs even.
- #3
Andrew Mason
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The proof is one line:lonelywizard said:
[tex]F = dp/dt = 0[/tex]
That is the definition of force. If the force acting is 0, dp/dt = 0 so p is constant.
AM
- #4
QuantumCrash
- 135
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I don't actually thinks that actually proves it. That just defines force. Other than practical experiments, or actually showing it works in every situations, I can't really think WHY it must be so.
Perhaps it is derived from elastic collisions, and kinetic energy is conserved. Perhaps not.
Perhaps it is derived from elastic collisions, and kinetic energy is conserved. Perhaps not.
- #5
Andrew Mason
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Conservation of momentum follows from Newton's first law. Since:QuantumCrash said:
[tex]F = dp/dt[/tex]
IF:
[tex]F = 0[/tex]
then: P = constant.
Why is Newton's first law true? It may not be. But to prove something, youi have to start with a premise. The premise is that F = dp/dt, Newton's first law. So far, no one has been able to show that it is not true.
AM
Last edited:
- #6
physics girl phd
- 930
- 3
Ohhh... the problem of asking to "prove" versus "verify/demonstrate". 
- #7
QuantumCrash
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Andrew Mason said:
Thats proof by contradiction that is. Since you can't disprove it that means its right. I suppose you might accept it that way. But what I am going about is more that you can't proof by induction and you can't really explain WHY momentum is conserved.