
Air Streams and the Floating Ball Effect
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Can a ball hover in midair without anything touching it? Point a hair dryer straight up and place a ball in the stream. The ball stays suspended and resists being pulled away.
You balance a table tennis ball or balloon above the airstream. Try pulling the ball slowly to one side. You feel a force tugging it back toward the center. Dangle tissue paper above the ball to trace where the air flows after it curves around the surface.
Tilt the dryer and notice the ball still floats. Move the setup toward a wall and watch the ball rise higher. The wall blocks air from escaping on one side and increases pressure beneath the ball. This same principle helps explain how airplane wings generate lift.
Hypothesis
The hypothesis is that the air flowing upward hits the bottom of the ball and slows down, generating a region of higher pressure that holds the ball up against the pull of gravity.
Method & Materials
You will need a blower, a spherical balloon or table tennis ball, and tissue paper. You will balance the ball above the airstream, pull it slowly out of the flow, and tilt the airstream to one side.
You will need a hair dryer, a balloon or table tennis ball, and tissue paper.
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See what’s includedResults
The experiment shows that when the ball is suspended in the airstream, the air flowing upward hits the bottom of the ball and slows down, generating a region of higher pressure. This high-pressure region of air under the ball holds the ball up against the pull of gravity. When you pull the ball partially out of the airstream, the air flows around the curve of the ball that is nearest the center of the airstream, creating an inward force on the ball.
Why do this project?
This experiment is interesting and unique because it demonstrates the Bernoulli principle, which explains why air flowing over a surface in an arc exerts less pressure on that surface. It also shows how air follows the surface of a sphere and why air pressure on the ball decreases, allowing the normal atmospheric pressure of the calm air on the other side of the ball to push the ball back into the airstream.
Also Consider
Experiment variations to consider include using a vacuum cleaner instead of a blower, and using a light-weight vinyl beach ball instead of a balloon or table tennis ball. Another variation is to move the blower and the ball toward a wall (try the corner of a room) and observe the great increase in height of the suspended ball.
Full project details
Additional information and source material for this project are available below.Related videos
These videos explain the science behind this project and demonstrate key concepts used in the experiment.
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