In a collision, how much mechanical energy is lost?

The answer to that is that it really depends. In the case of elastic collisions, there is of course no loss of mechanical energy. read more

In the case of elastic collisions, there is of course no loss of mechanical energy. In the case of an inelastic collision, I can't tell you how much energy is lost, but I can tell you a way of finding out how much energy is lost. In the case of an inelastic collision, energy is not conserved, so we cannot rely on the energy conservation law. read more

The kinetic energy, the energy of motion, before the collision is the sum of the energies of the two (or more) colliding objects. So, you must determine what that total is. It is a vector quantity, meaning it makes a difference in which direction the objects are traveling relative to each other. read more