- #1
lonelywizard
- 3
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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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SUMMARY
The discussion centers on proving the Law of Conservation of Momentum, emphasizing its relationship with Newton's first law of motion. Participants highlight that the equation F = dp/dt signifies that if the net force (F) is zero, the momentum (p) remains constant. While some argue that this definition does not constitute a proof, they acknowledge that the inability to disprove Newton's first law supports its validity. The conversation also distinguishes between proving and demonstrating the law through practical examples such as car accidents and elastic collisions.
PREREQUISITES- Understanding of Newton's laws of motion
- Familiarity with the concept of momentum (p = mv)
- Basic knowledge of calculus, specifically derivatives (dp/dt)
- Experience with elastic and inelastic collisions
- Explore practical experiments demonstrating conservation of momentum in car accidents
- Study elastic collision scenarios and their implications on kinetic energy conservation
- Investigate the mathematical derivation of Newton's first law
- Review the concept of proof by contradiction in physics
Students of physics, educators teaching mechanics, and anyone interested in the foundational principles of motion and momentum conservation.
- #2
QuantumCrash
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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:
F = dp/dt = 0
That is the definition of force. If the force acting is 0, dp/dt = 0 so p is constant.
AM
- #4
QuantumCrash
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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:
F = dp/dt
IF:
F = 0
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
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- #6
physics girl phd
- 930
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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.