To paraphrase an old saying, nothing is certain but death, taxes, and gravity. I added the third item to that list, of course, but it’s true. Even when we don’t want it to—especially when we don’t want it to—gravity is always there, and it always works. It’s reliable and infallible, and nobody but nobody can do anything about it. Sure, birds can fly and helium balloons can float, but birds have to work at it, and balloons eventually deflate—they have to come back down eventually. Every once in a while a spaceship breaks the surly bonds of gravity to soar into the cosmos, but it takes such titanic effort and expense that it’s impossible, on a practical level, for any of us to escape gravity’s grip.
Birds, balloons, spaceships…surely gravity can’t affect them all equally. Or can it?* This simple demonstration shows that gravity is an equal-opportunity inescapable force of nature.
If You’ve Got Shoes, You’ve Got Science
Well, technically, if you’ve got a shoe, a piece of paper, and a chair or something similar to stand on, you’ve got science. Start by crumpling that paper into a ball; tight or loose, doesn’t matter, really. Then take off a shoe, or steal one from a kid or whatever, and clamber up onto that chair. Carefully, of course.
With the shoe in one hand and the paper ball in the other, hold your arms out at shoulder height. Ask your observers (students or whomever) to guess which object will hit the ground first if you drop them at the same time. You’ll likely get mostly “the shoe,” a few “the paper” just because they’ll think it’s a trick question or something, and probably one little weisenheimer who’ll say “neither.” Keep an eye on that kid in the future. Maybe, maybe, maaaaybee, you’ll get one kid who says they’ll land at the same time. Keep an eye on that kid, too.
Tell the kids to watch closely, then drop both objects simultaneously. Plop! They’ll hit the ground at the same time. Because gravity.
La Science, S’il Vous Plaît
Both the shoe and the ball o’ paper land at the same time because the weight of an object doesn’t affect the rate at which it falls. This rate is constant—approximately 9.81 meter/second2. Whether it’s a piano or a toothbrush, everything falls at the same rate.
However, the shape of an object can influence the speed at which it falls. If you dropped an uncrumpled piece of paper, it would have fallen much slower, floating to the ground in a lazy back-and-forth swoop. This is because more air would hit its surface, causing increased friction. You can repeat the demo with a flat piece of paper and the same shoe to show your observers how this works.
- 365 More Simple Science Experiments with Everyday Materials, Judy Breckenridge, Anthony D. Fredericks, and Louis V. Loeschnig1988. ISBN 978-1579129675
* And don’t call me Shirley.