# Inelastic collision problem

## Homework Statement

I am doing this project and it asks me for the before and after velocity of a inelastic collision.

## The Attempt at a Solution

I have found the before velocity of both object which is 0 and 15 m/s, however i am trying to find the after velocities right now, the thing is they are not stuck together so their are two speeds. So far i have added my two momentum's to find the total momentum before collision. However, now i am stuck with a solution i cannot find.

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Have you been given the value of the coefficient of restitution?

I have found the before velocity of both object which is 0 and 15 m/s, however i am trying to find the after velocities right now, the thing is they are not stuck together so their are two speeds. So far i have added my two momentum's to find the total momentum before collision. However, now i am stuck with a solution i cannot find.
You have two equations , one for conservation of momentum and the other is for conservation of kinetic energy.
Because the kinetic energy is conserved in the elastic collision.
From them you can find the final velocities of the two objects.

By the way , it is an elastic collision , not inelastic.

haruspex
Homework Helper
Gold Member
You have two equations , one for conservation of momentum and the other is for conservation of kinetic energy.
it is an elastic collision , not inelastic.
The OP says it is inelastic, so work is not conserved. It may be that garr6120 has stated the problem incorrectly, but I see no reason to suppose so.

The OP says it is inelastic, so work is not conserved. It may be that garr6120 has stated the problem incorrectly, but I see no reason to suppose so.
Yeah! I too have doubt about that. But I think if the value of coefficient of restitution is given then that question can be solved even if the collision is inelastic.

The OP says it is inelastic, so work is not conserved. It may be that garr6120 has stated the problem incorrectly, but I see no reason to suppose so.
Oh ,, I thought that it is elastic since the two object doesn't stuck together ,,
I was wrong
:)

haruspex
Homework Helper
Gold Member
Oh ,, I thought that it is elastic since the two object doesn't stuck together ,,
I was wrong
:)
Right. To be honest, it has always seemed strange to me that 'elastic' is taken to mean perfectly elastic, i.e. no energy loss, and 'inelastic' for when there is any energy loss. It feels more natural to reserve inelastic for the case of zero coefficient of restitution and regard all nonzero restitution as varying degrees of elasticity. But there it is.

• Maged Saeed
I understand now, But in this question he didn't provide the coefficient of restitution .thus , the question is a little bit confusing .