Very Hard Maths Question!!!

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wass
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#1
Report Thread starter 18 years ago
#1
COULD ANYONE HELP (FROM M2):

A SPHERE OF MASS M1 MOVING WITH SPEED U1 COLLIDES DIRECTLY WITH A SIMILAR SPHERE OF MASS M2 MOVING WITH SPEED U2 IN THE SAME DIRECTION (U1>U2). THE COEFFICIENT OF RESTITUTION BETWEEN THEM IS e. SHOW THAT THE LOSS OF KINETIC ENERGY E DUE TO THE COLLISION SATISFIES THE EQUATION:

2(m1 +m2)E = m1m2(u1-u2){squared}(1-e{squared})

any help would be great sorry about the symbols.
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dazmanultra
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#2
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#2
We're not talking about point particles, right?

We're just getting on to kinematics of solids, I'll look through my notes for you.
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elpaw
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#3
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#3
its not that very hard, you just have to mess around with the algebra after you have your 3 basic equations and solve for E
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wass
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#4
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#4
all i have used is the equation for the loss of KE and the coefficent of restitution. i can not see how momentum works for this.

point particles? never herd of them i presume the spheres are modeld as perticles.
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elpaw
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#5
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#5
(Original post by wass)
i can not see how momentum works for this.
conservation of momentum:

m1u1 + m2u2 = m1v1 + m2v2

that's your third equation.
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wass
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#6
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#6
can some post a solution i can not do it, my teachers can not do it and it's buging me.
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username9816
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#7
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#7
(Original post by wass)
can some post a solution i can not do it, my teachers can not do it and it's buging me.
if your teachers cant do it yet they make u do it, then thats pretty scary.
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elpaw
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#8
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#8
i got this far:
Image
Image
the solution looks pretty similar, but i must have dropped an e somewhere.
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byb3
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#9
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(Original post by elpaw)
i got this far:
Image
Image
the solution looks pretty similar, but i must have dropped an e somewhere.
i personally hate these types of questions. The technique itself isn't that difficult, its just the number of variables increase the chances of you making an easy mistake. Looking at the kind elpaws working out is surely evidence enough!

Adam
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Eru Iluvatar
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#10
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#10
(Original post by wass)
COULD ANYONE HELP (FROM M2):

A SPHERE OF MASS M1 MOVING WITH SPEED U1 COLLIDES DIRECTLY WITH A SIMILAR SPHERE OF MASS M2 MOVING WITH SPEED U2 IN THE SAME DIRECTION (U1>U2). THE COEFFICIENT OF RESTITUTION BETWEEN THEM IS e. SHOW THAT THE LOSS OF KINETIC ENERGY E DUE TO THE COLLISION SATISFIES THE EQUATION:

2(m1 +m2)E = m1m2(u1-u2){squared}(1-e{squared})

any help would be great sorry about the symbols.
I'd be able to help if i remembered how to do this stuff, but i don't.
But i'm doing this sort of thing now, so i might be able to try it.
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elpaw
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#11
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#11
(Original post by byb3)
i personally hate these types of questions. The technique itself isn't that difficult, its just the number of variables increase the chances of you making an easy mistake. Looking at the kind elpaws working out is surely evidence enough!

Adam
i know, once you've got the 3 equations at the top, thats all the theory. the rest is all messy algebra which is bound to make you do mistakes. fortunately they wouldnt ask something like that in an exam (not A levels anyway), they would give you a few values for the variables.
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byb3
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#12
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#12
(Original post by elpaw)
i know, once you've got the 3 equations at the top, thats all the theory. the rest is all messy algebra which is bound to make you do mistakes. fortunately they wouldnt ask something like that in an exam (not A levels anyway), they would give you a few values for the variables.
lol, my last m2 exam with edexcel was a bit like that. There were so many e's it was like a rave.

Adam
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