Find energy in joules? When electron acquires speed of 10^6?

Question

In detail, thanks for answering x

Answer 1

Hi Charlie,

 

When you are talking about high-speed electrons, we need to determine whether or not we need to consider Special Relativity. The electron speed is v = 10^6 m/s, and the speed of light c = 3.0 X 10^8 m/s. 

 

v/c = 10^6 / 3.0 X 10^8 = 0.0033, which is a small enough speed ratio to not care about relativstic effects. So, we can use the classical formula for kinetic energy, 

 

KE = (1/2) mv^2

 

m = 9.11 X 10^(-31) kg is the mass of an electron.

 

KE = (1/2)(9.11 X 10^(-31) kg)(10^6 m/s)^2 = 4.56 X 10^(-19) J