I came up with last night and I couldn't figure it out. Can you actually predict what happens in a collision? For instance, suppose a truck and a toy duck is coming from opposite ends, they both have a velocity, now suppose they crash, it should be obvious that the collison isn't going to be elastic. But how do we know this? Is it because of the significantly large momentum of the truck? Suppose I give you another situation Situation #2 A truck and a car coming towards each other, with the same speed. And they clashed. What happens? 1) The truck has a greater momentum and hence will inelastically collide with the car and become one 2) Even though the truck has a greater momentum, they will collide and elastically bounce off each other How do we predict this? Please only use linear momentum. Use these M = mass of truck m = mass of car vtruck vcar vtruck + car vtruck' vcar' Situation # 3 (other) Suppose I throw a snowball at an 500-year-old oak tree and the ball sticks to the tree and eventually falls to the ground when it melts So that Mtree >> msnowball Now we have Mtreevtree + msnowballvsnowball = (Mtree + msnowball)v' But 0 + msnowballvsnowball = (Mtree + msnowball)v' 0 + msnowballvsnowball = (Mtree)v' For Mtree >> msnowball And that the tree doesn't move (maybe the roots sustained the net force impaled?) msnowballvsnowball = 0 But this doesn't make sense seeing neither are 0 Does this have to do with Newton's third law?