1. Spin each egg in turn on a plate. The egg that continues to spin for a longer time is the cooked one.
2. Now spin the eggs again, then quickly stop both of them. Then let go of both eggs. You will see that the cooked egg stays still but the raw one starts spinning again.
Why?
The contents of the egg have more inertia when they are raw, because they are in the form of a liquid. This inertia slows down the raw egg and that is why it stopped spinning before the cooked egg. In step 2, the liquid in the raw egg was still moving when you stopped both eggs, so that movement made the raw egg begin to spin again.
