Calculate the momentum

Question

Calculate the momentum of an electron if its kinetic energy is 10keV.

Answer 1

I'm going to answer this question using Newtonian physics instead of Relativistic physics. In reality, the answer changes a bit because the electron travels very fast and typically we would consider Relativity in the answer, but I'll assume you are talking in non-relativistic terms.

Kinetic Energy (E_K) is defined as 1/2 the mass times the velocity squared or:

E_K = 1/2mv²

You can look up the mass of an electron is a book or online. it is 9.109x10^-31 kg

You can also find the conversion of keV to joules, it is 1 keV = 1.60218x10^-16 joules

So 10 keV = 1.6022x10^-15 joules

So we can say, using E_K = 1/2mv² that:

1.6022x10^-15 = 1/2(9.109x10^-31)v²

v = √(2•1.6022x10^-15/9.109x10^-31) = 5.931x10⁷ m/s

Momentum is mass times velocity. So I bet you can find the momentum of the electron.