Easter Eggs

The hard-boiled eggs can be quickly separated from the soft-boiled eggs by placing them on a hard surface spinning them. The hard-boiled eggs will spin quickly and easily. The unboiled eggs will hardly spin at all.

The reason for this is that an unboiled egg has a fluid inside. When you try to spin the shell, the liquid core doesn't pick up the angular momentum as easily as a solid one. Instead, it sloshes about, like a bowl of soup would if you tried to spin it (Kids, don't try this on the good tablecloth!) So instead of the energy going into the spin, it goes into the chaotic motion of the liquid. The egg will first start to spin, then it will go into a wobble and settle down.

The energy that would have gone into the spinning motion doesn't really get lost. It gets turned into a small amount of heat inside the egg. The hard-boiled egg's energy eventually will become heat as well. As the egg slows down, it is losing energy to the air and surface it's on.