Two ice skaters, daniel (mass 70.0 kg ) and rebecca (mass 45.0 kg ), are practicing. daniel stops to tie his shoelace and, while at rest, is struck by rebecca, who is moving at 12.0 m/s before she collides with him. after the collision, rebecca has a velocity of magnitude 7.00 m/s at an angle of 52.1 ? from her initial direction. both skaters move on the frictionless, horizontal surface of the rink.

a what is the magnitude of daniel's velocity after the collision?

b what is the direction of daniel's velocity after the collision?

Cyclotrons are widely used in nuclear medicine for producing short-lived radioactive isotopes. these cyclotrons typically accelerate h- (the hydride ion, which has one proton and two electrons) to an energy of 5 mev to 20 mev. this ion has a mass very close to that of a proton because the electron mass is negligible—about 1 2000 of the proton’s mass. a typical magnetic field in such cyclotrons is 1.9 t. (a) what is the speed of a 5.0-mev h-? (b) if the h- has energy 5.0 mev and b = 1.9 t, what is the radius of this ion’s circular orbit?