An alpha particle of mass m m\,m and charge +2e+2e+2e enters a uniform magnetic field of magnetic flux density B B\,B at right angles to the field. The particle moves with a non-relativistic speed v v\,v in a circular path of radius rrr.
What is the number of complete revolutions made by the alpha particle in one second?
Be2πm\frac{Be}{2\pi m}2πmBe
πmBe\frac{\pi m}{Be}Beπm
Beπm\frac{Be}{\pi m}πmBe
2Beπm\frac{2Be}{\pi m}πm2Be