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AEROLAB: Information for the Teacher - Drag
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Planes with more drag fly more slowly than streamlined planes. Planes with more drag require more
thrust to counteract drag.
Consider an unmodified JETSTREAM that has an average speed of 4.6 m/s. After
drag is added (assuming that the thrust is the same) the acceleration will be less,
according to Newton’s Second Law, F=MA. Therefore, a plane with more drag
will travel a greater distance around the pylon while its speed increases to the
point at which it can lift off the ground.
A plane with more drag will fly slower and it will also fly at a lower altitude around the pylon. Most of
the energy of the plane is used to counteract greater drag and the plane does not have the needed energy to
climb to a higher altitude.
The pylon string applies centripetal force that counteracts the velocity and inertia of the plane. According
to Newton’s 3rd Law, the string and the plane pull with equal and opposite force. If the line were to break,
the plane’s inertia would cause it to fly off in a straight line.
Sample Data: The following table shows some likely results for a pylon plane with a radius of 2.1
meters:
1000 Turns on the
Rubber Motor
Without Yarn
With 0.5 meters of yarn
at the end of each wing
Liftoff
Around
Pylon
25 %
40 %
Average
Altitude
Average
Laps
Average Total
Distance
Average Speed
(meters/second)
~ 0.8 meters
~ 0.4 meters
5.8 laps
3.5 laps
76.5 meters
46.1 meters
4.6 m/s
3.9 m/s
Name _______________________________________
Class Period _____
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AEROLAB: Drag
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Background: When you wind up the rubber motor of a model plane, you are storing potential energy.
This energy is transformed into kinetic energy when you launch the plane. Drag, the resistance to forward
motion, is a by-product of the plane’s passage through the air, and it slows the plane down. Adding yarn
to a plane increases drag. If yarn is added to a plane (but thrust remains the same) the plane will accelerate
more slowly, thereby delaying takeoff according to Newton’s 2nd Law, F=MA. As thrust accelerates the
plane forward, the wings of the plane generate lift. Both lift and drag are proportional to speed squared.
Drag increases until it equals thrust, causing the plane to fly at a constant speed. When the plane flies
level and at constant speed, weight equals lift and drag equals thrust. Drag limits the speed of a plane. In
general, planes with more drag need more thrust to fly.
Directions: You will be adding yarn to your plane to study how the increased drag affects flight. Work
with your partner or group and choose one plane to study.
1) Finish this hypothesis: If drag increases, then… ___________________________________________
2-4) List at least three variables you should keep the same every time you test your plane.
5) The radius from the pylon to the fuselage = ________ meters
6) One revolution = Circumference =
2r = ___________ meters
7) Fly your JETSTSREAM without added yarn.
 Adjust the wing to balance the plane. Then mark the wing position with a pen.
 Wind your motor 1000 times with a winder.
 Release your plane and note the exact point of takeoff. Record the takeoff point on each circle below.
(The release point of the plane is represented by the dot at the bottom of the circle.) Meanwhile, have
another person in your group time how many seconds the plane flies in the air around the pylon while
a third person counts the laps in the air. Stop timing and counting laps the instant the wheels of the
plane touch down. Wind the rubber motor of the plane the same number of times for each trial.
Drag 3/9/06
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Name _______________________________________
Class Period _____
UNMODIFIED JETSTREAM
Trial 1
Trial 2
Trial 3
Averages
Laps =
Laps =
Laps =
Average Laps =
Seconds =
Seconds =
Seconds =
Average Seconds =
Takeoff = ___ %
Takeoff = ___ %
Takeoff = ___ %
8) Calculate the average speed of your JETSTREAM.
Average Speed =
Distance = (Average Laps x Circumference) = _______________ m/sec
Time
Average Seconds
9) Fly your JETSTREAM with added drag.
 Attach 50 – 80 cm of yarn to the tip of each wing. Adjust your wing so that it is back at the
marked location. Collect data using the same procedure as before.
JETSTREAM WITH ADDED YARN
Trial 1
Trial 2
Trial 3
Averages
Laps =
Laps =
Laps =
Average Laps =
Seconds =
Seconds =
Seconds =
Average Seconds =
Takeoff = ___ %
Takeoff = ___ %
Takeoff = ___ %
10) Calculate the average speed of your JETSTREAM with added drag.
Average Speed =
Distance = (Average Laps x Circumference) = _______________ m/sec
Time
Average Seconds
Drag 3/9/06
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Name _______________________________________
Class Period _____
11) What do the data show? Summarize.
12) _____ Which plane seemed to fly at a slower speed?
A) The plane without yarn was slower.
B) B) The plane with yarn was slower
13) _____ Which plane seemed to climb to a higher altitude?
A) The plane without yarn climbed to a higher altitude.
B) The plane with yarn climbed to a higher altitude.
14) ________________ In addition to increasing drag, what other variable is changed when yarn is added
to the plane?
15) _____You may have “flown” your hand out of a car window at fast and slow speeds.
Use your experience to answer this question: What happens to lift when the
car (or an airplane) slows down?
I) Lift Increases as the car (or plane) slows down
D) Lift Decreases as the car (or plane) slows down
16) How did the addition of yarn affect the takeoff distance?
17) Was the potential energy of your plane changed when yarn was added to it? Why or why not?
18-20) Why did the plane with yarn behave the way it did? Discuss the relationship between the plane’s
drag and speed. Also discuss what happens to the lift when yarn is added.
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