The students will identify, differentiate, and diagram the four principals of flight (weight, lift, thrust, and drag).
paper with a plane drawn on it
Introduction: This lesson builds the foundation for the rest of the unit so it is important to make sure that the students see the point in this lesson, and that they come to understand these concepts based on finding answers to their own student generated questions. Begin by asking the students what they know about flight. Some students may have a great knowledge of flight already because of a passion and curiousity that they have been exploring, use these students to raise enthusiasm among the other students. At some point, one of the students will ask something along the lines of:
How does a big heavy plane fly?
This is where the four concepts can be introduced.
is an obvious place to start. The students understand that the plane does weigh something, as do birds and other animals that fly. Explain that there needs to be a force to overcome this weight, and that force is called
. At this point, the ping pong ball demonstration from the Strategies section of this unit can be shown to illustrate how a plane is actually pulled up by the way air moves. Another valuable demonstration at this time would also be the homemade airfoil also discussed in the Strategies section of this unit.
2. After a brief discussion of how lift counteracts weight, the students should arrive at the conclusion that a plane must be moving forward in order for it to fly. Introduce the term
and describe that as the force that moves an airplane forward. As a result of the plane moving through air, however, there is the final force called
. Drag is air resistance acting on a moving plane. Explain to the students that is a bit like walking through water, it is hard to do, and the faster they try to move through the water, the more they have to work to overcome drag.
3. A good demonstration at this point is to take a candle (with the principal's permission and every possible safety precaution put in place) and place a piece of construction paper in front of the flame. Blow at the broad side of the paper and the students will notice that the flame dances around in all directions. Explain that this is drag, the air moves around in many directions behind the plane (the paper) and causes the plane to slow down or stop moving altogether. Then paperclip two sides of the paper together and stand it upright. Have the clipped end point to the flame and blow (gently) on the rounded side. The flame will now bend back gently. This indicates that there is very little drag because the air can move in a smooth path past the plane.
4. Give the students a piece of paper with a plane drawn on it. Have the students draw one arrow that points straight up, one that points straight down, one that points straight in front of the plane, and one that points directly out the front of the plane (as in figure i). Ask the students what they think the arrows might indicate. Most likely, one of the students will say that each arrow is one of the four forces. Have the students label the drawing. Depending on the level of the class, this can be done whole class, or individualized with different amounts of assistance, some students may find that a peer can explain it to them more clearly.
Closure: Once the students have the diagram clearly labeled, have them differentiate among the different forces. Encourage them to put the definitions of each force into their own words.
Extension: Make paper airplanes with the students, allow differentiations in design, supply students with paperclips and translucent tape if needed. With a sensitive classroom scale, weigh the planes. Have the students try to fly the planes using different amounts of 'thrust.' Students will begin to see that the heavier a plane is, the more thrust is needed for the plane to glide. This is not a great way to examine all four forces in isolated action, but students will begin to understand that a certain amount of speed is needed for the plane to glide successfully, and that the angle of attack changes how well the plane will glide. The angle of attack changes the drag on a plane. If the plane is launched at a steep angle upward, a great deal of force is needed for any kind of a successful glide.