TIME REQUIRED

Two to three 50-minute periods.

LESSON RATIONALE

Flight is a subject that affects students daily.  Good used in everyday life are transported by air.  Even if students have never ridden in an airplane, they may wonder how flight is possible.  Although airplanes are complex pieces of machinery, the fundamentals of the theory that makes flight possible are simple to understand.

LESSON DESCRIPTION

The first concept introduced is the idea of pressure differentials (the results of a high pressure and a low pressure acting upon a solid) and how they account for the lift of an airplane.  The Bernoulli equation is used to introduce this concept.  Since the equation can be solved using algebra, the students can see for themselves how pressure and velocity are interrelated.  Once the students understand this concept, they can learn why an airfoil (wing) of a correct shape will create lift.

Through the lesson, you will perform various demonstrations to clarify the main concepts.  The visualization helps reinforce the understanding of the physical phenomena that make flight possible.

MATERIALS

1. Classroom set of copies of the student reading, the Glossary for Chapter 3 and the Mathematical Glossary.
2. Several balloons.
3. Drinking straw and partially filled glass of water.
4. For the hair drying demonstration (demonstration #1): hair dryer, piece of oak tag or light cardboard, thumbtack, piece of paper.
5. For the airfoil demonstration (demonstration #2): electric fan, piece of Styrofoam about 6" long and at least 1-1/2" thick, two 12" lengths of wire coat hanger, 18" length of dowel about 1/4" in diameter, glue.
6. Optional: classroom set of copies of Figures 1-3, which follow the student reading.

LEARNING OBJECTIVES

Students will:

1. Substitute values for variables in an equation.
2. Solve for variables within an equation.
3. Understand that equations can represent physical concepts.
4. Understand and apply the concepts of lift and pressure (as related by Bernoulli's equation) and thrust and drag, as these relate to flight.  See the Glossary for Chapter 3 below.

In addition, students will have to understand constants, subscripts, factors, factoring, squares, exponents, and cross multiplication.   These terms are listed in the Mathematical Glossary.

ENRICHMENT ACTIVITIES

1. Assign the problems below for homework.  Distribute the assignments to different students or teams.  Set aside a class period for reports of the results.
2. Design an experiment using a wind tunnel and an airfoil to demonstrate the principles learned in this lesson.
3. Select five different shapes and decide which makes the best airfoil.
4. Design and build your own wind tunnel, to include a clear panel for viewing.  Use a fan to move the air across dry ice to observe the air flow over the airfoils.  (Ask for permission to work with your science teacher in her or her lab to construct this device.)
5. Go to your library and ask your librarian to help you select a book on flight.
6. Search the internet to find out more information about flight.

SUGGESTED PROCEDURES

1. Provide motivation for the lesson plan by throwing a Frisbee or glider around the room.
2. Ask students why they think planes are able to fly.
3. Introduce the concept of pressure differentials, using a drinking straw.  Sucking on a straw causes the pressure above the liquid in the straw to fall below the pressure of the atmosphere, which pushes on the liquid in the glass and forces the liquid up into the straw. (See the student reading).
4. Distribute the student reading to the class.
5. Use the hair dryer experiment (demonstration 1) to introduce Bernoulli's equation.
6. Go over the meaning of each of the variables in the equation.
7. Work through the problem in the student reading with the class.
8. Point out to the students that their calculations show that the slower speed is accomplished by higher pressure and the faster speed by lower pressure.
9. Show the airfoil cutout or draw a copy on the chalkboard.  Use the picture to explain why air must travel faster on the top than on the bottom of the airfoil (wing), as a result of the airfoil's shape.
10. Do demonstration 2 and relate it to the preceding student problem.  Ask students to explain how the relatively faster velocity of the air above the airfoil affects the pressure on the top and bottom on the airfoil.  Ask how the power pressure on the top of the airfoil affects the flight of the airplane.
11. Introduce the concept of thrust.  Tell the students that thrust is what causes the plane to move upward.
12. Blow up a balloon, but do not tie the end.  Explain that the air pressure inside the balloon is higher than the pressure outside.  Release the balloon and watch it fly all over the room.  Point out that the air is under high pressure inside the balloon and as it escapes through the nozzle it pushes the balloon forward.  Related this to the thrust of an airplane engine.

GLOSSARY FOR CHAPTER 3

Airfoil
A suitably curved sheet of material (such as a wing of an airplane) which, because of its shape, creates lift when air flows over it.

Angle of attack
The angle at which an airfoil is moved forward into the air.  Up to a point, the steeper the angle of attack, the more lift is created.  However, too steep an angle of attack will cause the air on the upper surface to become turbulent, thus slowing it down instead of speeding it up, thereby creating a cessation in lift, which will cause the aircraft to fall.

Drag
The resistance of the surface of the airplane fuselage to the forward motion of the aircraft.

Fuselage
The body of an airplane.

Pressure
The force of the air as it pushes on a surface.  It is measured either in pascals or in pounds per square inch.

Pressure differential
The difference between the pressures on opposite sides of an airfoil, which creates the lift for the airfoil.

Thrust
The force that causes a forward motion in an aircraft; it may be provided by jet engines or propellers.

Wind tunnel
A small tunnel designed for use in a laboratory in which a stream of air can be blown on an airfoil.  Because the tunnel is closed on its sides, the stream of air can be delivered forcefully and without interference from drafts.