What is the magnetic field in that region of space?

Question

A cosmic-ray proton in interstellar space has an energy of 95 MeV and executes a circular orbit having a radius equal to that of Mercury's orbit around the sun (5.8 £ 10 m).

The proton has a charge of 1.60218 £ -19 C and a mass of 1.67262 £ -27 kg. What is the magnetic field in that region of

space? Answer in units of T.

Answer 1

First, convert eV into J by multiplying by 1.6 x 10^-19. That will give you the kinetic energy. Using the formula K = ½mv², solve for the velocity. When you have that, use the formula r = mv / qB. Solve for the magnetic field.