A neutron at rest breaks up to a proton and an electron, and energy is released and appears as kinetic energy of the proton and electron. The mass of a proton is approximately 2,000 times the mass of an electron. What is the ratio of the kinetic energy of the proton and the electron?


이 문제인데요 양성자와 전자의 운동량이 같다는 점을 이용해서 풀라는데 왜 둘의 운동량이 같은지 설명을 못하겠어요,,,