Question

what role does friction play in an elastic and inelastic collision experiement?  

Answer 1

In elastic collision, there's both energy and momentum conservation applies. And friction cause energy loss so in elastic collision there's no role of friction force, we totally ignore the losses due to friction force.

Also in inelastic collision we do not apply momentum conservation still we use enery conservation so in this collision also, we ignore the loss due to friction force.

If we dont ignore friction then we can apply conservative of momentum but energy can't be conserve.

I am confused what friction you are talking about, if it's the friction force between the molecules then may be shape of object can deform, so conservative of momentum doesn't valid.

But if you talking about friction by air or plank whatever, then I have already explained the case.