Question

which would be more effective, a hammer that collides elastically with a nail, or one that collides perfectly inelastically? Assume that the mass of the hammer is much larger that that of the nail.

Answer 1

When the hammer hits the nail elastically, the velocity of the hammer will be nearly same as its initial value and the nail will move nearly double the initial velocity of the hammer.

When they collide perfectly inelastically, both the hammer and nail will move with a velocity nearly equal to the initial velocity of the hammer. So the perfectly elastic collision is more effective.