An electron has a rest mass of 0.511 MeV. From this information one can conclude that the rest mass of an electron is A) 9.08 $\times$ 10^-31 kg B) 8.82 $\times$ 10^-14 kg C) 2.94 $\times$ 10^-22 kg D) 5.68 $\times$ 10^-12 kg E) None of these is correct.

Question

Quizplus · Accepted Answer

The rest mass of an electron is given in units of energy, MeV (mega-electron volts) in this case. To convert it to kilograms, we need to use Einstein's famous equation E=mc^2, where E is the energy equivalent of the mass m, and c is the speed of light. Rearranging the equation to solve for mass, we get m=E/c^2. Plugging in the rest mass of an electron (0.511 MeV) and the speed of light (299,792,458 m/s), we get m=0.511/(299792458^2)=9.11x10^-31 kg, which is closest to choice A.

An Electron Has a Rest Mass of 0 ×\times× 10-31 Kg B) 8

An Electron Has a Rest Mass of 0 $\times$ 10^-31 Kg
B) 8