1. Particle one of mass m initially moves to the right at v. Particle two of mass 2m is initially at rest. After they undergo an elastic collision, particle one moves directly down. What is the final speed of particle two?
2. A 0.280-kg ball makes an elastic head-on collision with a second ball initially at rest. The second ball moves off with one fourth the original speed of the first ball. What is the mass of the second ball?