Question

A Lithium-5 atom at rest decays into a proton and an \alpha particle with the release of 3.15×10-13 J of kinetic energies total of the proton and the \alpha particle. Determine the velocities of the proton and the alpha particle after the decay. You can assume the masses are m _\alpha = 4m_p = 6.64×10-27 kg.

Answer 1

The velocity of the alpha- particle is 4.356×10⁶ m/s.Here ,velocity of the alpha-particle, V_{​​​​a} ≈ 0.01 C , C is the velocity of light ,hence the factor

1/ {1-(V_{​​​​​​a}/c)²}½≈1

Therefore here I was not used relativistic theory .