Sci/Tech: Three curious things

OK, hints and answers are in the next entry, but see what you make of these, before you take a peek:

Which egg is which?

You have two eggs in your refrigerator. One of them has been hard-boiled, while the other egg is raw. How can you tell which egg is which?

Put one of the eggs on a dinner plate, and spin it fast. Then stop it, let it go, and watch what happens. Then do the same with the other egg, stopping it as it is spinning fast, and letting it go again. Why does this happen?

Strange matter

Mix one and a half cups of cornflour with one cup of water in a bowl. Slowly dip your finger into the gooey mixture; then try slapping it hard with your hand or a heavy spoon. What happens? Why?

Then try letting some of the goo flow across a piece of rubber sheet cut from an old rubber glove. Stretch the rubber slowly, then stretch it fast, and notice what happens each time.

Get a pair of scissors, and pour some of the mix from a spoon. Can you snip the stream with the scissors? (Think: would I ask you this if you couldn’t do it, somehow?)

Pile driver

Fill a plastic jar with rice and carefully jab a blunt knife into the rice five or ten times. The rice will settle a bit, so add more rice. Continue until no more rice can be added. Then quickly jab the knife into the rice and lift. What happens? Why?

Can you work out why this item is called “Pile driver”?

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