If an electron in the lab has a kinetic energy equal to twice its rest energy, what is its speed in the lab?
A) 0.91c
B) 0.89c
C) 0.94c
D) 0.84c
E) 0.87c

Question

Quizplus · Accepted Answer

The total energy of the electron is three times its rest energy (rest energy + twice the rest energy as kinetic energy). Using the relativistic energy-momentum relation, E = γmc², where γ = 1/√(1-v²/c²), we find that γ = 3. Solving for v gives v ≈ 0.94c.

If an Electron in the Lab Has a Kinetic Energy