This is a problem that though I've solved has had me racking my brains trying to figure out whether or whether not I actually understand what I'm doing..here goes:(adsbygoogle = window.adsbygoogle || []).push({});

Particles A and B have massmand are moving in the same direction along a line, A with speed3uand B with speedu. They collide and after the impact they both move in the same direction, A with speeduand B with speedku. The coefficient of restitution ise

a) show that e = (k-1)/2

b) Deduce that 1 =< k =< 3

c) Find the loss in kinetic energy in terms of m, k, and u.

As I said above...reaching the answers to these questions is not the problem...the bit thats bothering me is that before getting to the bit where I could solve part a) I had come to the conclusion that k can only = 3. My reasoning is as follows:

The total momentum of the system before impact is 3mu + mu, and given that I know the momentum of A after impact (mu) I can say that:

mu + kmu = 4mu...k = 3...the other way I look at it is as follows:

B imparts an impulse on A that changes it's velocity from being 3mu to mu, in doing this A must impart the same impulse to B such that:

-(mu - 3mu) = (kmu - mu)...k still = 3 (the minus sign is because J acts in different directions)

The question implies however that e and k are not already determined and can take any value beween 0,1... 1,3 respectively.

The only conclusion that I can reach however is that this is wrong and that given the mass of both objects, their initial speeds and either the value of e or just the speed of either A or B any other values are forced...this question stated otherwise

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# Homework Help: Collision Question problem with question itself!

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