Question

Suppose you have two eggs, one hard-boiled and the
other uncooked. You wish to determine which is the
hard-boiled egg without breaking the eggs, which
can be done by spinning the two eggs on the floor
and comparing the rotational motions. (a) Which egg
spins faster? (b) Which egg rotates more uniformly?
(c) Which egg begins spinning again after being
stopped and then immediately released? Explain your
answers to parts (a), (b), and (c).

Answer 1

a)The boiled egg would have higher spin than a raw egg because the raw egg resists getting its spin on account of its internal fluid i.e. it has a higher moment of inertia.

b)A raw egg tends to wobble and hesitate, because the liquid yolk and white are different densities, flowing from side to side as the egg spins. A solid, hard-boiled egg, on the other hand, spin smoothly.

c)When you stop a raw egg with your hand, then quickly let go. If the egg remains at a complete stop, it’s hard-boiled. But if it begins to move again after you take away your hand, it’s raw. It is because when you stop a spinning raw egg, the shell applies force on the liquid inside. The liquid, in turn, applies an equal and opposite force on the shell, nudging it back into motion.