Whenever important physicists are discussed, galileo galilei, isaac newton, and albert einstein seem get the most attention. however, as you’ve seen, galileo formulated or refined many of his discoveries and theories based on the findings of others who came before him, including aristotle and nicolaus copernicus. likewise, newton claimed that he “stood on the shoulders of giants” in developing his work. what physicist do you think have been overlooked?

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?