Created 5-30-07
Bernoulli’s Demonstrations
The main goal of these modules is to provide a basic visual demonstration of Bernoulli’s
principle that when the velocity of a fluid increases, its air pressure decreases. This can be
demonstrated in two ways: first with two hanging ping pong balls and with a ping pong ball in a
funnel.
Hanging Ping Pong Ball
1. Hang two Ping Pong balls approximately two inches apart as shown in the following
picture:
Figure 1: Hanging Ping Pong Balls
2. Blow air through a straw between the two balls. They will collide with each other
because the air velocity is greater between the two balls than on the other sides.
Therefore, the air pressure will be lower between the balls than on the other sides
which will cause the balls to move towards each other.
Funnel and Ping Pong Ball
If an air hose is available, this principle can also be demonstrated using one ping pong ball and a
funnel.
1. Hold the funnel upside down and direct the air hose into the bottom of the funnel as
shown in Figure 2.
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Created 5-30-07
Figure 2: Funnel Set-Up
2. Hold the ping pong ball in place before starting the air flow.
3. The air flow should hold the ball in place as shown in Figure 3.
Figure 3: Ping Pong Ball in Funnel
The air being blown into the funnel will move around the surface area of the ball and create an
area of pressure above the ball that is less than the pressure below it. This leads to an upward
force called “lift” that will prevent the ball from falling out of the funnel.
Card and Spool
1. Put a pin through an index card and put the pin through the hole of a wooden spool.
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Created 5-30-07
2. Hold the card and spool as shown in Figure 4.
Figure 4: Card and Spool
3. Blow up through the spool. If done correctly, the card should stay on the spool no
matter how hard the air is being blown because the air velocity is greater below the card
than above it. Thus, the air pressure will be greater above the card than below it, which
will keep the card from blowing off the spool.
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