Momentum and energy is always conserved.
p= γmo v, where p is the relativistic momentum, v is the speed of the particle and mo is its mass as measured by an observer at rest with respect to the particle.
Rest energy, Eo = moc2
Total energy, E = γmoc2
Kinetic energy, KE = γmoc2 – moc2
∆E = ∆mc2
E = γEo
K.E = (γ – 1)Eo
E2 = p2c2 + (moc2)2
For particles that have zero mass, such as protons, mo = 0, E = pc
1 eV = 1.602 x 10-19 J
1 eV : energy required to accelerate an e- through a potential difference of 1 volt.
1 u = 1.66 x 10-27 J