Question Regarding Impulse and momentum

[tiny-tim]

hmm …

have you done conservation of momentum?

if so, what is the equation for conservation of momentum for rubber bouncing off a wall on ice (ie, no foundations, so the wall can slide along the ice, but the wall is initially stationary)?

 

[haruspex]

Lead... Change in momentum= final - intial = 0-mv=-mv i guess? opposite to the direction of original propagation...

Rubber bullet... mu-mv = m(u-v) ??

I was trying hard not to confuse you on this. You can think in terms of speeds or in terms of velocities. Because all the movement is in the same straight line, but in opposite directions, the difference is how the sign is handled. In my previous post I defined u as a speed, but you seem to be using velocities, so I'll stick with that.
If u and v are velocities measured in the same direction then the momenta are mu and mv, and the change in momentum is mu-mv, as you wrote. But note that u will be negative. So if you compare the magnitude of -mv (change in momentum for the lead) with that of m(u-v) (change in momentum for the rubber), which is larger?

 

[kashan123999]

I don't know :( i am confused as hell,Tommorow is my physics exam,please tell me the answer,i can develop critical skills later on :D I am a pakistani so that really makes me a rote learner and far far behind the world sorry :D so,what is the detailed answer?

 

[tiny-tim]

have you done conservation of momentum?

 

[kashan123999]

have you done conservation of momentum?

yep,initial momentum = final :@ change in momentum = 0

 

[tiny-tim]

yep,initial momentum = final

ok, so try applying total initial momentum = total final momentum to rubber bouncing off a wall on ice (ie, no foundations, so the wall can slide along the ice, but the wall is initially stationary)