THE PRESSURE'S OFF II- FLIGHT
In this lesson and its extension the students will have an opportunity
to learn what allows air planes to fly, why birds can fly, and why people
can't. This lesson contains several hands-on activities that teach Bernoulli's
Principle and allows the students to implement the understanding of it.
The group will construct a giant hot air balloon that can be launched using
only a hair dryer.
Scientific Eye #8: Lighter than Air
Students will be able to:
- define and demonstrate Bernoulli's Principle
- measure to the nearest centimeter
- give examples of Bernoulli's Principle at work
- describe what happens when air is heated
Bernoulli's Principle I
Bernoulli's Principle II
- 1 funnel top of a two liter bottle per group of three
- 1 small balloon per group of three
- 1 hair dryer per group of three
- 5 cm X 20 cm piece of paper
- measuring device
- Hot Air Balloon
- 8 55 gallon commercial garbage bags per group
- cellophane tape per group of four
- measuring device per group of four
- scissors per group of four
- hair dryer per group of four
Ask the children "Have ever taken a shower curtain stick
to you when the water is running in the shower?" "Does it look
like someone is outside the shower pushing the curtain in?"
NOTE TO TEACHER: The expected response it that the students would
notice the shower curtain moving inwards as though there was someone on
the outside pushing it in.
After the students have given their responses, ask them what actually caused
the curtain to move inwards. At this time don't give any explanation as
to what was happening to cause the curtain to move inwards.
The title of this video is "Lighter than Air" and
we are going to see if there is anything that is truly light than air. Group
one, I want you to see if you can figure out what is causing the shower
curtain to go inwards when the shower is running. Group two, I want you
to see if you can identify three different heat sources used to launch hot
air balloons. Group three, please see if you can identify the problem with
making a small hot air balloon. And group four, identify the different types
of hot air balloons that were shown.
BEGIN the video Scientific Eye #8 where the boy is blowing
up the balloon and PAUSE after "Guess what is holding up this
unidentified object." Allow the children to guess. RESUME the
video and pause after "And this beach ball?" Allow the children
to guess again. RESUME the video and PAUSE after "Cut
off the air stream and the ball drops." Give the groups the funnel
made from the two liter bottle, the balloon and a hair dryer. Instruct the
students to inflate the balloon and tie it off so no air can escape. Put
the balloon inside the funnel and direct the hair dryer so it will blow
into the mouth of the two liter bottle. Turn the hair dryer on and observe
what happens. Hold the balloon inside the funnel as the large end is pointing
toward the floor. Turn the hair dryer on and observe what happens. Discuss
the results and why they happened.
NOTE TO TEACHERS: This is Bernoulli's Principle in action. Air moves
faster around the balloon causing the air pressure to be less than the pressure
below the balloon allowing the balloon to not be affected by gravity.
FAST FORWARD without sound (the rationale for no sound is
that what is being said does not address the curved shape of the objects)
to the eagle in flight. PAUSE at that point and ask the students
to observe the shape of the bird's wings. RESUME the video and PAUSE
as the glider is taking off. Ask the students to observe the shape of the
gladder wings. Ask what the eagle and glider have in common.
NOTE TO TEACHER: Both the bird's wings and the gladder wings are
curved on top and straight across the bottom.
Give each child a piece of paper and ask them to measure and cut a piece
that is five cm by twenty cm. Instruct the students to lay the paper over
their index finger. Tell them that they will place the paper under their
lower lip and blow. Before they do this, ask them to predict what will happen
with the paper when they blow air over it. After they have made their prediction,
have them do the activity and observe what does happen.
NOTE TO TEACHER: The paper will come up and flap in the wind. The
reason for this is again, Bernoulli's Principle. Air travels faster over
a curved surface, allowing the air pressure to be greater on the bottom
of the paper that it is on the top so the paper is pushed up. This is what
creates lift allowing airplanes to fly.
FAST FORWARD to where the clouds are forming in the sky. PAUSE
after the question "How could we use hot air to lift something up?"
Allow students to answer. RESUME the video and PAUSE after
the question "Will the hot air from a hair dryer be enough to lift
this trash bag?" Allow the students to make a prediction. RESUME
the video and pause after the question "What will happen when the bin
liner is filled with hot air?" Allow the students to make a prediction.
RESUME the video and PAUSE after the question "What will
happen when you blow out the flame and the balloon cools down?" Allow
the students to make a prediction. RESUME the video and PAUSE
after the flame was blown out. Discuss all of the students' predictions.
RESUME the video and PAUSE after each of the following questions
allowing the students to make predictions: "Do you think these liners
are a sensible material to use?" "Does the color of the material
make any difference?" "What sort of material would you choose
to use to make a big balloon?" How would you make enough hot air to
fill it?" RESUME the video after each question to allow the
students to make observations about their predictions. STOP after
"But that project had to be put off to another day." Discuss with
the group all of their observations. Go back to the focus for viewing and
ask each group to tell the answer to their question. Discuss any of the
questions the students might have.
Using the information you have just gained, we are going to
design hot air balloons made from trash bags. I will be handing out the
directions for this activity. Please read through the activity before you
begin any part of it. Please assign jobs within your group so that all are
actively involved. (See Appendix A.)
NOTE TO TEACHER: You will probably have to lead the group through
this activity one step at a time. When all of the groups have completed
the hot air balloon, it is launch time. Each group will need a hair dryer
and possibly an extension cord. If you have a gym or a room with high ceilings
you might choose to do this inside. This can also be done outside, but you
would probably want to have a tether rope on the balloon to keep it from
going too high.
Invite a hot air balloonist to come to you school for a demonstration
if possible and a talk about his/her experiences while using the hot air
Invite an airplane pilot to come to you class to talk about the importance
of Bernoulli's Principle in flying airplanes.
Have each student write a lab report on the activity they did in the post-viewing
Do research on Bernoulli's Principle
Social Studies/ Arts:
Write a report on the use of hot air balloons in the history of the world.
Science: Make the hot air balloons using a different colored garbage bag.
Put a tether on the hot air balloon. Using the tether, measure how high
the balloon goes and then do the same process to see if color does make
a difference as to how high the balloons will go.
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