a) Two marbles are pressed together with a light ideal spring between them, but they are not attached to the spring in any way. They are then released on a frictionless horizontal table and soon move free of the spring. As the marbles are moving away from each other, which of the statements about them are true?
(a) Only the momentum of the marbles is conserved,
(b) only the mechanical energy of the marbles is conserved,
(c) both the momentum and the mechanical energy or the marbles are conserved,
(d) the kinetic energy of the marbles is conserved. Explain your answer.
b) A student fires a rifle while standing with the butt of the gun against their shoulder. The forward momentum of a bullet is the same as the backward momentum of the gun. Explain why it isn't as dangerous to be hit by the gun as by the bullet.
C) A skater is standing still on a frictionless ice rink. A friend throws a ball straight at them. In which of the following cases is the largest momentum transferred to the skater?
(a) The skater catches the ball and holds onto it.
(b) The skater catches the ball momentarily, but then drops it vertically downward.
(c) The skater catches the ball, holds it momentarily, and throws it back to the friend.