Detecting the Hard-Boiled Egg

What to do: Spin each egg. Note what

happens. Then touch each egg lightly

while it is spinning.

What happens: Two of the eggs

wobble, but one spins. The spinner is

the hard-boiled egg. When you touch

the spinning hard-boiled egg lightly it

stops spinning completely. The raw

eggs move again after you have tried to

stop them.

Why: The loose yolks and whites in the

raw eggs resvolve slowly because of

inertia, the tendency of an object to

continue at rest or in motion. This causes

the raw eggs to wobble and to continue to

move even after you tried to stop them.

The solid white and yolk cause the hard-

boiled egg to respond more quickly.

YOU NEED

•two raw eggs •one hard-boiled egg

And…There is a critical spinning speed below

which the egg stays horizontal. This is about ten

revolutions per second - roughly the speed it

reaches after a firm flick of the wrist.

As the egg rises, its spinning form is more

compact, making it whirl more quickly. "It’s like

when a turning figure-skater speeds up by pulling

in his or her arms," Nickel says.

The egg’s initial orientation doesn’t matter, and

it will pirouette on either pole.

WhyHard-boiled eggs spin faster and longer than raw eggs. A hard-boiledegg is a solid. It spins easily.The raw egg has liquid and yolk inside the shell. The shell and liquidof the raw egg do not move together as do the shell and solid of thehard-boiled egg. The liquid inside sloshes around, causing the egg towobble. When the eggs are stopped by touching them, the motion ofthe shell and the solid inside the boiled egg is stopped. But the rawegg starts to spin again because even though the shell is stopped,the liquid inside continues to spin, and this ‘motion’ starts the shellspinning again.

CAUTION: After handling raw eggs, wash your hands andany materials touched by the eggs. Raw eggs can containharmful bacteria. Discard eggs after completing theexperiment.

Take An Egg for a Spin II