In a thundercloud there may be an electric
charge of 47 C near the top and −47 C near
the bottom. These charges are separated by
approximately 1.8 km.
What is the magnitude of the electric force
between them? The Coulomb constant is
8.98755 × 10^9 N · m^2
/C^2
.
Answer in units of N.

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?