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Can coefficient of restitution be negative?

Hi so I've just had a mechanics exam and one of the questions asked to calculate the coefficient of restitution. I calculated it and got -0.85 but in the multiple choice there was an answer for -0.85 and an answer for +0.85. I've never seen the coefficient be negative in any questions I've done before so I'm doubting my answer now. Could someone clear this up please?
Original post by Unknown-99
Hi so I've just had a mechanics exam and one of the questions asked to calculate the coefficient of restitution. I calculated it and got -0.85 but in the multiple choice there was an answer for -0.85 and an answer for +0.85. I've never seen the coefficient be negative in any questions I've done before so I'm doubting my answer now. Could someone clear this up please?


Apparently not

http://www.a-levelphysicstutor.com/m-momimp-coeffrest.php
Reply 2
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Unknown-99
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Original post by Kevin De Bruyne


Ffs. There's never been a question where the answer has come out negative before and I'm 100% sure I did the calculation right I've triple checked it. I hate looking over the exam paper after the exam and realising I dropped 4/5 easy marks it's so annoying! Anyway, thanks for your help.
Original post by Unknown-99
Ffs. There's never been a question where the answer has come out negative before and I'm 100% sure I did the calculation right I've triple checked it. I hate looking over the exam paper after the exam and realising I dropped 4/5 easy marks it's so annoying! Anyway, thanks for your help.


No worries, remember your performances average out and you'll be fine.
there is case where the coefficient of restitution is negative.There is also a case where it is greater than 1. Suppose you consider a collision where one object hits another and completely passes through and comes out of that object, this is when coefficient of restitutuion is negative. you can calculate and check. The case when coefficient of restitution is >1 is when a explosion occurs
Yeah, so the thing is that 'e' (or coefficient of restituition) can never be negative. The range of 'e' is only from 0 to 1 depending upon the type of collision that takes place. If it's a perfectly elastic, e = 1 and if it's perfectly inelastic, e=0. All the other values vary differently because the type of collision it undergoes is more or less close to such collisions.Hope I could help.Cheers mate.
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Original post by rohitkosuru
Yeah, so the thing is that 'e' (or coefficient of restituition) can never be negative. The range of 'e' is only from 0 to 1 depending upon the type of collision that takes place. If it's a perfectly elastic, e = 1 and if it's perfectly inelastic, e=0. All the other values vary differently because the type of collision it undergoes is more or less close to such collisions.Hope I could help.Cheers mate.


They've probably solved it now, but feel free to help out in any more recent threads.

I'm closing this one :smile:

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(edited 5 years ago)

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