Question

A radioactive nucleus is at rest when it spontaneously decays by emitting an electron and neutrino (as shown in the figure below ). The momentum of the electron is 8.11 x 10−19 kg·m/s and it is directed at right angles to that of the neutrino. The neutrino's momentum has magnitude 5.08 x 10−19 kg·m/s. In what direction does the newly formed (daughter) nucleus recoil? Let the electron direction be along the positive x-axis and find the direction of nucleus recoil with respect to the electron's direction.
What is its momentum?