bernoullis__lab by cuiliqing


     Title - Introduction to Bernoulli's Principle

       Basic premise of Bernoulli's equation: In fluid dynamics, Bernoulli's principle
       states that, an increase in the speed of the fluid occurs simultaneously with a
       decrease in pressure or a decrease in the fluid's potential energy.[
       Actual equation:

The Coanda effect: is the tendency of a fluid jet to be attracted to a nearby surface.

Objective: Students will observe and document behavior of materials that undergo a
change in fluid velocity nearby.


Station #1: Hold a piece of paper between your thumb and forefinger, as shown. Now
blow over the paper.

Station #2: Place the two ping-pong balls at a distance of 2.54 cm apart on the table. Take
your straw and gently blow a stream of air between the two. Put your ping-pong balls
away in the designated place for the future station or lab group.

Station #3: Blow up two balloons and tie each one to a string. Hold the balloons a few
inches apart and try to blow them together. Can you do it? What happens? Try different
ways of blowing on the balloons to see what happens.

Station #4: Place the ping-pong ball in the funnel. Use the technique demonstrated at the
beginning of class to "blow the ping-pong ball out" from the top as diagrammed on the
board. Attempt to use the same procedure when the ping-pong ball/funnel system is
upside down. Can you defy gravity with Bernoulli? Hold a Ping-Pong ball over a flexible
straw, as shown. As you blow into the straw, let go of the ball. What happens? Play
around with holding the straw in different ways. For example, can you tilt the straw and
still keep the ball in the air?
Hint: You can use any lightweight ball or a small balloon, but you may need to blow

Station #5: Place a ping-pong ball in a 50 ml beaker and blow across, down… and
observe the results
Station #6 Stick a pin through the middle of a card from below. Place the spool over the
pin. Hold the card and pin in place with one hand; hold the spool with the other. Blow
through the spool and let go of the pin and card. What happens?

Station #7 Fluids, such as air and water, change speed as they flow between and around
objects. To see how this happens, build this tiny stream channel. Tape pencils on a cookie
sheet so that they make a channel that starts out wide, then narrows. Drape the pencils
and cookie sheet with plastic wrap. This creates a water-proof channel. Now barely tilt
the cookie sheet against the sink and slowly pour soapy water into the channel. Does the
speed of the water change? How? When? Hint: You may want to add small scraps of
paper or Styrofoam to the water to help your observations.

Station #8 Hold an index card close to a stream of moving water. Describe the results

Analysis and conclusion:

Station #1:
1) What happened to the paper when you placed a velocity of air parallel and above it?

2) What happened to the paper when you placed a velocity of air parallel and below it?

Station #2:
3) Write Bernoulli's equation below and circle the variables that you witnessed in this

4) From the above equation, how did the variables observed affect one another? (i.e.: the
buoyant force on an object is larger when a larger volume of fluid is displaced by the

Station #3:
5) Why did the results occur?

6) Name three examples of how Bernoulli's principle can be used in a device at home.

Station #4:
7) Why could you not "blow the ping-pong ball out"?
8) Did you succeed in defying gravity? Draw a diagram of this station below and show all

Station #5:

9) What happened in this experiment? Why?

Station #6

10) Explain the results using a force diagram showing all forces.

Station #7

11)Why does a streams velocity increase as the width of the stream decrease?

Station #8:

12) What happened in this experiment? Why?

1) Relate what happens when a large truck is passing your car on interstate 90.

2) Julie is riding in a car with her large family and, to her disgust, grandpa lights up a
cigar. The car is filled with smoke and finally Julie asks him to crack open his window.
How does the pressure outside the car now relate to the pressure inside the car? What
happens to the disgusting smoke particles? (two questions = two answers).
3) Use diagrams to explain one reason why airplanes can fly. Use the words pressure,
velocity and force as well as vector arrows.

4) You are on the interstate and a convertible passes you and the cloth top appears bulged
out. Or you roll down the windows in an older car (poor tracks for the windows) and
when you roll it up it has moved out explain either situation.

To top