An evacuated tube uses an accelerating voltage of 40 kv to accelerate electrons to hit a copper plate and produce x rays. non-relativistically, what would be the maximum speed of these electrons?

The energy acquired by the electrons due to the accelerating voltage is given by:

where
is the electron charge
is the accelerating voltage
Substituting the numbers into the formula, we find


If the electrons start from rest, this value corresponds to the final kinetic energy of the electrons:

Keeping in mind the equation for the kinetic energy:

where  is the mass of one electron, we can rearrange the formula to calculate the final speed of the electrons: