Can momentum be conserved in an inelastic collision?

[phattestlewt]

From what i understand, momentum is conserved, even in inelastic collisions, when there are no external forces (i.e. friction, wind resistance) action on the system.

BUT! energy is not conserved in an inelastic collision, where as in an elastic collision, energy is conserved.

Am I right in thinking this??

Thanks!

And what's an easy way to conceptually think about Impulse. I'm have a hard time with that topic.

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[milski]

Yes, for a closed system, moment is always conserved, period. You are also right about elastic/inelastic collisions. If you want to be completely precise, the energy that we are talking about in this case is kinetic energy. Even in inelastic collisions the energy does not disappear - it becomes some of potential energy, for which you cannot account easily.

You can think of impulse as a way for objects to trade momentum. You can change the momentum of a body by the same amount by applying a small force for a long time or by applying a large force for a short time. The impulse is what abstracts these details and tells you how by how much the moment was changed, without having to worry how exactly that was achieved. For constant forces, the impulse is very easy to calculate, p=F.t where F is the force and t is the time for which it was applied. Note that just like momentum and forces, impulse is also a vector quantity - it has a direction and a magnitude.