1. The problem statement, all variables and given/known data A mass m moving at velocity v collides with a stationary target having the same mass m. Find the maximum amount of energy that can be released as heat and sound. 2. Relevant equations KE = (1/2)mv^2 Momentum = mv 3. The attempt at a solution I guessed at 1/2KE (or (1/4)mv^2)) and got it right. But I am trying to think of reasons why no more than half the kinetic energy can be released as heat and sound can't think of it.