A uranium nucleus at rest undergoes fission and splits into two fragments, one heavy and one lighter. Which fragment has the greater magnitude momentum?

Question

A) The heavy one

B) The lighter one

C) Both have the same momentum

D) Impossible to say

Why is C) the answer?

Answer 1

Conservation of Momentum says that no matter how the atom splits, the final momentum of both particles add up to the original momentum. The original nucleus was at rest, which means zero momentum. In other words, it doesn't matter what the momentum of one piece is, the other has to be equal and in the opposite direction so that they cancel each other when added together.