Download Time Average Seconds

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AEROLAB: Information for the Teacher - Weight
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According to Newton’s Second Law, F=MA, a heavier plane with the same thrust will experience a smaller
acceleration. Therefore, a heavier plane will travel a greater distance around the pylon, while its speed increases
to the point at which it can lift off the ground. Conversely, Newton’s 2nd law predicts that lighter planes with the
same thrust will have a greater acceleration and will takeoff sooner. Planes with more weight require more lift to
fly. When a plane flies level and at constant speed, lift equals its weight.
A heavier plane usually will fly at a lower altitude around the pylon. A heavier plane will have more kinetic
energy (but less potential energy) than a plane with less weight. The flight time and travel distance of a heavier
plane will be shorter than that of a lighter plane.
The pylon string applies centripetal force that counteracts the inertia and velocity of the plane. According to
Newton’s 3rd Law, the string and the plane pull with equal and opposite force. If the pylon string were to break,
the inertia of the plane would cause it to fly off in a straight line.
Consider a JETSTREAM that has an average speed of 4.6 m/s and a mass of 15 grams. More energy is required
to take off and achieve altitude. If the energy is held constant (at 1000 turns on the rubber motor) the plane
cannot climb as high, the distance flown is less and the flight time is also less.
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
No Extra Weight
With 1 penny
With 2 pennies
Liftoff Around
Average
Pylon
Altitude
25 %
~ 0.8 meters
38 %
~ 0.5 meters
50 %
~ 0.35 meters
Average
Laps
5.8 laps
4.9 laps
2.2 laps
Average Total
Distance
77 meters
61.2 meters
27.2 meters
Average Speed
(meters/second)
4.6
~4.6
~4.6
Two important notes:
1) The average speed of the plane should remain constant regardless of weight. This is because the JETSTREAM
has no movable control surfaces (rudder, ailerons, elevators); the trim never changes and, in general, the plane
flies at the same angle of attack. Keeping the number of turns on the rubber motor constant also ensures that the
average speed remains constant for each flight.
2) Be sure to place the penny over the center of gravity, about 1/4 of the way back from the leading edge of the
wing. If the penny is placed too far back on the wing, the plane will be tail-heavy, increasing drag and
decreasing the average speed of the plane.
Name _______________________________________
Class Period _____
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AEROLAB: Weight
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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. As thrust accelerates the
plane forward, the wings of the plane generate lift. As a plane goes faster, lift increases.
According to Newton’s 2nd Law, F=MA, if mass is added to a plane and thrust remains the same, the
plane will accelerate more slowly, thereby delaying take off. Lift is equal to weight when a plane flies
level and at constant speed. For example, a 15-gram plane generates 15 grams of lift. A JETSTREAM
with added mass will have greater kinetic energy (but less potential energy) than a lighter
JETSTREAM.
Directions: You will be adding pennies to the plane to study how added weight affects flight. Work
with your partners and choose one JETSTREAM to study.
1) Finish this hypothesis: If weight increases, then…
2) List at least three variables you should keep the same every time you test your plane.
3) In addition to weight, what variable is also affected when you add pennies to your plane?
4) Calculate the distance your plane will fly around the pylon:
The radius from the pylon to the fuselage = ________ meters
One revolution = Circumference =
2r = ___________ meters
Weight 3/9/06
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Name _______________________________________
Class Period _____
5) Fly your JETSTREAM without any added weight
 Adjust the wing to balance your plane. Then mark the wing position with a pen. Wind your motor
1000 times.

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.
UNMODIFIED JETSTREAM
Trial 1
Trial 2
Trial 3
Averages
Laps =
Laps =
Laps =
Average Laps =
Seconds =
Seconds =
Seconds =
Average Seconds =
Takeoff = ___ %
Takeoff = ___ %
Takeoff = ___ %
6) Calculate the average speed of your JETSTREAM.
Average Speed =
Distance = (Average Laps x Circumference) = ____________ m/sec
Time
Average Seconds
7) Fly your JETSTREAM with added weight
 Add 1 or 2 pennies to the exact center of gravity (about 1/4 of the way back
from the front of the wing) and collect data. Adjust your wing so that it is
back at the marked location. Collect data using the same procedure as
before.
JETSTREAM WITH ADDED MASS
Trial 1
Trial 2
Trial 3
Averages
Laps =
Laps =
Laps =
Average Laps =
Seconds =
Seconds =
Seconds =
Average Seconds =
Takeoff = ___ %
Takeoff = ___ %
Takeoff = ___ %
Weight 3/9/06
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Name _______________________________________
Class Period _____
8) Calculate the average speed of your JETSTREAM with added weight.
Average Speed =
Distance = (Average Laps x Circumference) = ____________ m/sec
Time
Average Seconds
9) How did the addition of weight affect the takeoff distance?
10) Why did the heavier plane fly the way it did? Discuss the relationship between its greater weight,
kinetic energy and potential energy
11) How did the addition of weight affect the flight time?
Weight 3/9/06
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