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A: Conservation of Momentum for Pulley System

XcoderXThe term going around the corner here just means that there is conservation of momentum as this is a single, closed system. Momentum is $mv$, mass multiplied by velocity. Since the mass was added during the movement of the pulley, momentum is conserved. This means that the initial momentum, $m...

user1583209
user1583209
Conservation of momentum and conservation of energy are not the same thing usually. You should make this clear in your answer.
XcoderX
XcoderX
Well, it follows from conservation of momentum that there is conservation of energy
user1583209
user1583209
Are you talking about this specific example of in general?
XcoderX
XcoderX
In general for the typical pulley questions
Jp McCarthy
Jp McCarthy
Thank you for your answer. The textbook does not use conservation of energy. Edit to come.
This does not answer the question. Please see the edit.
user1583209
user1583209
17:11
Can you be more clear about what your question is? This is not a place to ask such open ended questions like: "explain how pulleys work" $m_1u=m_2v$ is momentum conservation. What is not clear about this?
Jp McCarthy
Jp McCarthy
I will edit further.
@user1583209 I edited.
Sorry @XcoderX this does not answer the question that I asked. To my mind the vectorial nature of momentum means that it should be more like $4u-3u=4v-5v$.
XcoderX
XcoderX
I am afraid i do not understand what you are looking for
Jp McCarthy
Jp McCarthy
You are incorrect straightaway by saying that conservation of momentum implies conservation of energy. This is false.
XcoderX
XcoderX
Why so? Which part of your edit isnt answered?
user1583209
user1583209
@XcoderX: Apparently the question is: Why is the momentum of a pully with two masses moving with velocity $v$ equal to $(m_1+m_2) v$ and not $m_1 v - m_2 v$ (as it would by vector addition of the momenta of independent/unconnected masses)?
Jp McCarthy
Jp McCarthy
17:11
@user1583209 yes this is the correct question.
XcoderX
XcoderX
Is it better now? @JpMcCarthy?
Jp McCarthy
Jp McCarthy
Why can you say the velocity is $v$ when one particle goes up and one goes down?
user1583209
user1583209
I will also attempt to answer this.
XcoderX
XcoderX
in $m_1v-m_2v$ velocity is also v.
Jp McCarthy
Jp McCarthy
@XcoderX thanks for your efforts. I reckon user1583209 will be able to help from here.
XcoderX
XcoderX
17:11
By velocity v, it means one side is moving down at v. So velocity v is the speed. What do you think, @JpMcCarthy

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