Problem with perfectly inelastic collisions.

[Cherryboba]

Two trucks, one twice as heavy as the other, collide head on (assume it's one dimensional and easy ;) ) and the collission is perfectly inelastic. If it was perfectly inelastic there would be no kinetic energy left, and therefore no velocity. How do the trucks manage to conserve momentum by moving in the direction of the smaller truck if they have no energy?

Please help out, I've been searching for days.

 

[zhermes]

An inelastic collision isn't necessarily one in which all of the kinetic energy is lost. Its simply one in which the kinetic energy isn't necessarily conserved.

Inelastic collisions are determined by conservation of momentum alone. In your example, if both trucks are going at the same speed, they would have a resulting velocity (one third of the initial).