physics...elastic head on collisions?

[princess]

1. In the experimental discovery of the neutron (the electrically neutral "brother" of the proton ) the ratio of the velocity of the recoiling (struck) proton over the velocity of the incident neutron was 0.9689. What was the ratio of the neutron mass over the proton mass? (Assume an elastic head-on collision).

2.An object makes an elastic head-on collision with another "target" object which is initially at rest. If the ratio of incident mass over target mass is 0.8647 what is the velocity of the incident object after the collision in multiples of its incident velocity ? Give the result with the appropriate sign taking the incident velocity as positive

3.A billiard ball with a velocity of 13.5 m/s makes an elastic head-on collision with another ball (same mass) which is initially at rest. Calculate the velocity of the struck ball after the collision