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Make a Ball Float on Air
by Lindsey Boardman, Photographs by Tim MacKay
This contraption demonstrates what physicists call the Bernoulli effect, which also explains how the wings of airplanes provide lift. But kids will just call the hovering ball amazing.
- Materials
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- 1-liter plastic bottle
- hair dryer with a "cool" or "cold" setting*
- cardboard box a few inches taller than the hair dryer
- duct tape
- craft knife (adults only)
- table-tennis ball
- Instructions
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Cut the bottom from a plastic bottle and cut a slit in the top section of the bottle. Measure to see if the bottle and hair dryer assembly will fit well in the box: place the bottle base upside down inside the box, place the hair dryer on top of it, and place the top section of the bottle over the dryer nozzle.
The mouth of the bottle should be a couple of inches taller than the box. Trim the top section to shorten it, if needed. -
Tape the top section to the dryer nozzle, overlapping the bottle's cut edges for a snug fit. -
Lay the bottle base and the dryer in or on the box to see where to cut the hole for the dryer handle and cord. (The bottle base will hold up the dryer and allow more airflow.) Cut the hole with a craft knife. -
Cut a hole for the top of the bottle. Place the dryer assembly into the box. -
For airflow, cut holes along the sides of the box near the base. If you'll be able to reach the dryer's power switch once the box is closed, tape the box shut. If you can't, cut an access hole in the side of the box. Set the box upright, plug in the dryer, and switch it on.
Place a table-tennis ball on the jet of air. Try gently tossing the ball onto the air jet, or see how far you can tilt the box before the ball falls.
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- Notes:
- * Safety note: Don't set the hair dryer on "warm" or "hot," as that could create a fire hazard.
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