OCR Momentum
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OCR MomentumA block of mass 3kg travelling at 5ms-1 catches up another block of mass 7kg travelling at 2 ms-1 along the same line and the same direction.
The difference between the speeds of the two blocks after the collision cannot be greater than the difference of the speeds before the collision. Deduce that the speed of the first block after the collision must satisfy the inequalities 0.8<=v1<=2.9
I had v2=(29-3v1)/5, and v1-3<=v2<=v1+3, which eventually leads me to 14<=8v<=44. This clearly isn't right, but I really don't know what to do. Help appreciated. -
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Re: OCR MomentumDefine a number e such that(Original post by Julii92)
A block of mass 3kg travelling at 5ms-1 catches up another block of mass 7kg travelling at 2 ms-1 along the same line and the same direction.
The difference between the speeds of the two blocks after the collision cannot be greater than the difference of the speeds before the collision. Deduce that the speed of the first block after the collision must satisfy the inequalities 0.8<=v1<=2.9
I had v2=(29-3v1)/5, and v1-3<=v2<=v1+3, which eventually leads me to 14<=8v<=44. This clearly isn't right, but I really don't know what to do. Help appreciated.
. Work from there
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Re: OCR MomentumWhy do you have it over 5?(Original post by Julii92)
I had v2=(29-3v1)/5
You also need to know that the speed of separation must be >=0. -
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Re: OCR Momentumm1u1 + m2u2=m1v1 + m2v2(Original post by ghostwalker)
Why do you have it over 5?
You also need to know that the speed of separation must be >=0.
3x5 + 7x2 = 3v1 + 5v2
29=3v1+5v2
29-3v1=5v2
v2=(29-3v1)/5
How does the speed of separation being >=0 help? -
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Re: OCR Momentum(Original post by Julii92)
m1u1 + m2u2=m1v1 + m2v2
3x5 + 7x2 = 3v1 + 5v2
29=3v1+5v2
29-3v1=5v2
v2=(29-3v1)/5
The inequality you have, although it gives two limits (if I recall), only one of them matches the restriction you're aiming for.How does the speed of separation being >=0 help?
You need the additional bit to get the second limit.Last edited by ghostwalker; 28-06-2012 at 16:36. -
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Re: OCR MomentumAh. Now I feel silly.
Okay, I'll have a go at using this.(Original post by ghostwalker)
The inequality you have, although it gives two limits (if I recall), only one of them matches the restriction you're aiming for.
You need the additional bit to get the second limit.
