Karen K. Kennedy, chemistry and physics teacher, T.C. Williams High School, Alexandria, Virginia.
Students will understand the following:
1. An increased speed of airflow over a surface results in a decrease in air pressure over that surface.
2. Air moves faster over a cambered, or arched, surface than over a flat surface.
3. Together, these two facts explain how an airplane lifts into the air and stays in the air.
In addition to research materials on flight and a computer with Internet access for the whole class, the following materials should be available for each group:
Two sheets of paper
Two empty soda cans
Transparent drinking straw
A cup of water
1. Review with your students what they have learned about the principles of flight. Then let them know that they are about to perform a series of simple experiments that will demonstrate the principles that make it possible for an airplane to lift into the air and remain aloft.
2. Divide the class into groups, providing each group with the materials listed above.
3. Instruct the groups to perform the following brief experiments. Before each experiment, have group members predict the result.
- Hold two sheets of paper so that they are hanging vertically with their surfaces facing each other, close together in front of your mouth. Now blow in between the papers, and observe the result. (The sheets of paper will move closer together.)
- Lay two empty soda cans on their sides, parallel to each other, and fairly close together on a table or desk. Holding a drinking straw between the cans and parallel to them, blow through the straw. What happens to the cans? (They will move closer together.)
- Cut a transparent drinking straw into thirds and hold one segment upright in a cup of water, with the top of the straw segment above the surface of the water. Blow across the top of the straw and observe what happens to the water in the straw. (The water level will rise.)
4. Discuss with the class as a whole what they can infer from their experiments. Encourage them to offer reasons for their results. If necessary, explain that increased speed of airflow over a surface causes a decrease in air pressure over that surface. Because of the decreased pressure between the sheets of paper and between the soda cans, the objects moved closer to each other; less pressure was pushing them apart. Likewise, because less pressure was holding the water down in the straw, the water level went up.
5. Continue the discussion by asking students to relate what they have learned to an explanation for how a plane lifts into the air. When you remind students that a plane first gathers speed on the ground before it takes off, they should be able to infer that the increased speed of airflow over the wings causes a decrease in pressure over the wings.
6. Finally, pose the following questions: “Why doesn't the increased speed of airflow underthe wings cause an equal decrease in air pressure?” and, “Wouldn't the speed of airflow have to be faster overthe wings than under to make the plane take off?” To help students answer this question, have them visualize the shape of an airplane wing. You might also ask them to visualize the shape of a bird's wing. They are both cambered, or arched upward.
7. Assign each group to use research materials to answer the questions you have posed and write a brief answer and explanation, accompanied by a labeled diagram. They should discover that air moves more quickly over an arched surface than over a flat surface. The speed of airflow is therefore faster overthe wings of a plane (or bird) than under, causing a decrease in pressure over the wings, but not under them.
8. Challenge students with one more question: “What would happen if a plane stopped moving in midair?” Students should be able to infer that it would crash; a constant airflow over the wing is necessary to keep the plane aloft.
Expect older students to produce longer, more detailed scientific explanations for flight and aerodynamics. For these students, you may want to omit the experiments.
DISCUSSION QUESTIONS: 1. Discuss the impact flight has had on history and global development. Consider such areas as travel, defense, commerce, and information.
2. Discuss why humans have been obsessed with flight since our earliest history. Are aircraft today good enough to satisfy this obsession or do you think we will continue to try to fly like the birds do?
3. Discuss the idea of millions of people boarding aircraft and flying without having any idea of why the plane stays in the air. Does this seem reasonable? Are there other activities we take part in on a regular basis that we don't understand completely?
4. Discuss the idea of flying with almost total reliance on a computer system. Can you see advantages to this? Can you see any drawbacks? Describe how activities such as driving a car are becoming more and more automated. Are you willing to turn control over to a computer?
5. Discuss the importance of using experimental aircraft such as the Pathfinder to study our atmosphere, especially the stratosphere.
6. Discuss whether or not we can continue to push the envelope with technology and reduce the time of travel between different areas of our globe. How would our world be different without the ability to go long distances in very short periods of time?
EVALUATION: You can evaluate your students on their explanations using the following three-point rubric:
Three points:accurate information; clear wording; logical organization
One point:some inaccurate information; some unclear wording; organization unsatisfactory
You can ask your students to contribute to the assessment rubric by determining what information should be included in the explanation.
EXTENSION: Fabulous Flying Machines!
Assign students to work individually or in groups to produce oral or written reports on one specific type of aircraft. Reports should include the distinguishing characteristics, usage, range, and estimated cost of the types they choose. If the whole class is involved, you should end up with information about a wide variety of flying machines.
The four principles that govern the motion of an object in flight are lift, weight, thrust,and drag. Each force has an opposite companion. Lift is an upward force, while weight is the downward force of gravity; likewise, thrust propels an object forward, while drag exerts a backward force. Each of these forces can be graphically represented by an arrow with a plus sign at the point. Inviting students to work in pairs, instruct each partner draw a diagram of an airplane. One diagram should use arrows to show lift and weight; the other should use arrows to show thrust and drag. Partners can take turns explaining to each other how each force affects a plane in flight.
SUGGESTED READINGS: The Simple Science of Flight: From Insects to Jumbo Jets
Henk Tennekes, MIT Press, 1996
The step-by-step explanations in this work emphasize the consistency of the fundamental aerodynamic principles that underlie the flight of both animals and objects. This book's unique approach is its consistent intermingling of nature and technology throughout the text and the diagrams to explain the mechanics of flight.
The Smithsonian Book of Flight
Walter J. Boyne, Wings Press, 1996
The evolution of the technology by which man has attempted to master flight is documented in these works, which draw heavily upon the collections of the Smithsonian Institution's National Air and Space Museum.
WEB LINKS: NASA's Allstar Network: Aeronautics Learning Laboratory for Science, Technology, and Research
Become an aeronautical engineer with this interactive flight tutorial from NASA. Rich in vocabulary and scientific principles with diagrams and MPEG movies to help us understand the inventions that help humans fly.
The Paper Airplane Hanger
Start an aeronautics competition at your school and learn the principles of flight with the many downloadable paper airplanes at and from this Web site. Which student can design and build the fastest paper airplane? The slowest? The farthest-flying?
National Air and Space Museum
Take your students on a cyberspace field trip to America's number one flight museum. Have students gather information as they walk through the halls of the virtual National Air and Space Museum in Washington, DC.
Flapping Wings! The Ornithopter Home Page
Ornithopters are flying mechanical devices that imitate the actions of a bird in flight. From Leonardo da Vinci to now, find all kinds of pictures and plans for building these robot type avians.
The Baals Wind Tunnel
Construction plans for your own classroom wind tunnel are provided by Lego and NASA at one the best free Sci/Tech curriculum sites on the Web.
A slightly arched surface.
And by cambering it, in other words giving it the shape of this bird's wing, with some curvature in it, you can get a sensation of even more lift.
Spectacular stunts, such as rolls and loops, performed in an airplane or glider.
But aerobatic planes are designed to fly upside down.
The orientation of an aircraft's axes relative to a reference line or plane, such as the horizon.
So you can fly the plane inverted almost in the same attitude with the same nose position as you can when you are upright.
The state or quality of being exact or accurate.
It takes precision and skill to turn cartwheels in the sky.
The region of the atmosphere above the troposphere and below the mesosphere.
It flew five miles high on its first altitude test and in future flights it will climb even higher into the stratosphere.
ACADEMIC STANDARDS: Grade Level:
Understands motion and the principles that explain it.
Knows that laws of motion are used to calculate precisely the effects of forces on the motion of objects; the magnitude of the change in motion can be calculated using the relationship F=ma.
Understands the nature of scientific inquiry.
Knows that conceptual principles and knowledge guide scientific inquiries; historical and current scientific knowledge influence the design and interpretation of investigations and the evaluation of proposed explanations made by other scientists.
Understands the nature of technological design.
Knows that a solution and its consequences must be tested against the needs or criteria the solution was designed to meet.
Understands the interactions of science, technology and society.
Knows that technological knowledge is often not made public because of patents and the financial potential of the idea or inventions; scientific knowledge is made public through presentations at professional meetings and publication in scientific journals.