How fast is a particle moving if its kinetic energy is equal to its rest energy?
A) 0.00
B) 0.57 c
C) 0.75 c
D) 0.87 c
E) 0.50 c

Question

Quizplus · Accepted Answer

The equation for kinetic energy is K = (γ - 1)mc^2, where γ is the Lorentz factor, m is the rest mass, and c is the speed of light. Setting K equal to m c^2 and solving for γ gives γ = 2. Plugging this value of γ back into the equation for velocity v = c√(1 - 1/γ^2) gives v = 0.87c. Therefore, the particle is moving at 0.87 times the speed of light.

How Fast Is a Particle Moving If Its Kinetic Energy