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Flying circus of physics

Flying Circus of Physics Samples

Run or walk in the rain?

Should you run or walk when crossing a street in the rain without an umbrella (Fig. 1-1)? Running certainly means that you spend less time in the rain, but it also means that you may be intercepting more of the rain drops. Does the answer change if a wind blows the drops either toward or away from you?

Woodpeckers and concussion

A woodpecker hammers its beak into the limb of a tree to search for insects to eat, to create storage space, or to audibly advertise for amate. During the impact, the rate at which the head slows is about 1000g’s (1000 times gravitational acceleration). Such a deceleration rate would be fatal to a human or at best severely damage the brain and leave the person with a concussion. Why then doesn’t a woodpecker fall from a tree either dead or unconscious every time it slams its beak into the tree?

Circular water-flow pattern in a sink

When a smoothly flowing water stream from a faucet hits a flat sink with an open drain, why does a circle form around the impact point, with deeper water on the outside of the circle?

Cocktail-party effect

In a small party with people standing and talking in pairs, each member of a pair stands at a “socially acceptable” distance from the other and the two can hear each other without any trouble. However, if the density of people in the room increases, why does hearing become more difficult, and what does each member of a pair do in response? Why can a voice still be distinguished? You might notice these same effects in many other environments, such as a noisy restaurant or subway car.

Wintergreen glow in the closet

You and a friend first adapt your eyes to darkness for about 15 minutes in a closet or outside on a moonless night. Then have your friend chew a wintergreen Life Saver candy (a candy in the shape of a marine lifesaver and infused with the oil of wintergreen) with the mouth as open as possible so that you can see inside. Why does each bite initially produce a faint flash of blue light, and why do later bites fail to produce the light? (If you don’t want to eat the candy, squeeze it with a pair of pliers until it fractures.) Why does tonic water have a faint blue tint?

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