Neutron Decay.? A neutron at rest decays (breaks up) to a proton and an electron. Energy is released in the decay and appears as kinetic energy of the proton and electron. The mass of a proton is 1836 times the mass of an electron. What fraction of the total energy released goes into the kinetic energy of the proton?
Solution 101P Step 1: The neutron was at rest initially and decays into a proton and an electron. The conservation of momentum tells that, m v = m v + m v ---------------------(1) n n p p e e Here the subscripts n,p and e stands for neutron, proton and electron. This implies, 0 = m vp pm v e e 1836 m v e p v = e e v = ve p 1836 The minus sign indicates that the particles will travel in opposite direction, because this is the only way to conserve the momentum and it is trivial too.