A 50 kg student stands on a 4 kg skateboard at rest. The student catches a 9 kg backpack moving with a horizontal speed of 2 m/s in the direction the skateboard is free to roll.
How fast will the student and the skateboard move after catching the backpack, assuming friction is negligible? Round your
final answer to the hundredths place (two decimal places) (no zero before the decimal)

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?