Morning, I was thinking about a simple example of inelastic collision: A ball of mass m1, moving with a certain velocity v1, collides and sticks with another mass m2, at rest. The whole system (m1 + m2) will then move with a certain speed v3. If we take m1=m2, so that after the collision we have a single mass of 2m1 mass, by the conservation of momentum, v3 = v1/2. If we work out the kinetic energy of the system before and after the collision, we have K(after) = K(before)/2. The question is...where does the other half of kinetic energy goes to? In such a collision, must we necessarily expect losses in terms of heat and sound, or can we find that other half transformed in some sort of "gluing energy"? Cheers, Luke.