Question

Speed of an Electron

What is the speed of a 677 eV electron?

What is the speed of a 3.50 keV electron?

Answer 1

Solving this formula for v, we get:

v = ?[(2)(KE)/(m)]

In order for this equation to work, we need to use standard units, which means converting the electron volts into Joules.

1 electron volt = 1.6x10^-19 Joules.

The mass of an electron is 9.11x10^-31 kg

So 677ev = 1.08x10^-16 J
and 3.5 keV = 5.6x10^-16 J

a) v = ?[(2)(KE)/(m)]
v = ?[(2)(1.08x10^-16 J)/(9.11x10^-31 kg)]
v = 1.613x10^7 m/s

b) v = ?[(2)(KE)/(m)]
v = ?[(2)(5.6x10^-16 J)/(9.11x10^-31 kg)]
v = 3.194x10^7 m/s