## Perfectly inelastic collision and inelastic collision

1. The problem statement, all variables and given/known data

Two gliders move toward each other on a frictionless linear air track.

Glider 1, mass = 0.5kg , velocity = 2m/s (to the left)
Glider 2, mass = 0.3kg , velocity = 2m/s (to the right)

After collision, glider 2 moves away (to the left) with final velocity of 2m/s.

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The question I want to ask is that, I read up on wikipedia, saying perfectly inelastic collision will result in the two objects sticking together and moving with a same final velocity.

However in this question, I found out the final velocity for glider 1 to be v = -0.4m/s, which doesn't support what Wikipedia has since glider 2 moves to the left with 2 m/s. So I'm thinking maybe the question given is NOT a perfectly inelastic collision, can anyone clear my doubts about this?

2. Relevant equations

m1v1 + m2v2 = m1u1 + m2u2

3. The attempt at a solution

substituting masses and velocities into the above equations will get me v1 = -0.4 m/s

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Hi,
The question directly states, if I understand you correctly that,
 After collision, glider 2 moves away (to the left) with final velocity of 2m/s.
Which implies that, once one of them has started to move separately, you can no longer consider it as a "perfectly" inelastic interaction between them. Rather, there could be a loss of kinetic energy due to other factors, but not such that would prompt them to coalesce.
I hope that helps,
Daniel

 Collision is not perfectly inelastic.