Mechanics> Does total momentum of a system mean the ...

Does total momentum of a system mean the vector sum of all the momentum?

Raisinten , 10 Years ago

Grade 11

8 Answers

Neeti

Last Activity: 10 Years ago

Yes, Since momentum is a vector you can’t simply add the momentum of different particles. You have to add them by using the vector method. And total momentum of a system is the vector sum of the momentum of all the constituents of the system.

Please feel free to ask any follow up question and approve the answer if you like it :)

Raisinten

Last Activity: 10 Years ago

If that is true, then in the gun and bullet example given in the momentum page should have mv-MV=0 as, if we take v, velocity of bullet in the +ve dir., the V is -ve.

Neeti

Last Activity: 10 Years ago

That’s exactly what is done. Initial momentum zero, finally bullet moves in one direction and if it is assumed to be positive direction then the gun recoils and moves in the opposite direction so MV1 – mv = 0 and therefore MV1= mv .

that’s how it is solved :) In Every momentum question, you have to consider the direction, ALWAYS .

Raisinten

Last Activity: 10 Years ago

But it is solved as MV=-mv.

Raisinten

Last Activity: 10 Years ago

http://www.askiitians.com/iit-jee-physics/mechanics/conservation-of-momentum.aspx

Neeti

Last Activity: 10 Years ago

You’re getting it wrong. See here they’re saying that the negative sign indicates the opposite direction of motion. Means thev’ve done it with respect to the positive x. They have not already assumed that the gun will move in -ve direction. But what i’ve done is, i’ve already assumed that the gun will move in the negative direction hence i’ve assumed it be be -v directly.

acha let me explain it to you in hindi,

Maine pehle se assume kia hai ki recoil hone pe gun opposite direction me jayegi. isilie maine pehle hi -v kar dia gun ke velocity ko. But link me they haven’t assumed anything.

And look at it this way, mv = M(-V) means V is is opposite direction, I’ve already assumed that the V which i’m using in equation is -v, that’s why my final equation doesn’t have –ve sign,

but i can also rewrite it as mv = M (-V ),it’s the same thing.

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Raisinten

Last Activity: 10 Years ago

Well, I understand English far better than Hindi, I am Bengali (I don’t speak much in Hindi). Thanks. I have got it and I have another doubt regarding a pendulum, I have posted it.