Typically, in a fission reaction, the nucleus split into two middle-weight nuclei of unequal masses. Which of the two (heavier or lighter) has greater kinetic energy? Which one has greater linear momentum?
-The lighter part will have more kinetic energy.
There can be 2 cases, if the nucleus is at rest, then the two parts will have same linear momentum. If the nucleus is not at rest, then the heavier one will have more linear momentum (as kinetic energy is inversely proportional to momentum).