Aerodynamics

Carole Janda                   O. A. Thorp Scholastic Academy
                               6024 W. Warwick Ave.
                               Chicago IL 60634
                               312-534-3640

Objectives:

     Demonstrate skill in hypothesis formulation, identification and control of 
variables, data collection, organization and interpretation of data.
     Discover and understand the basic principles of aerodynamics, including
the roles and identity of natural forces involved.
     Discover how the force of GRAVITY is overcome by the curved shape of an 
airplane wing and air pressure.
     Discover why air pressure is lower moving across a curved surface vs.
a straight surface, creating LIFT. (Bernoulli's Principle).
     Discover why an airplane will stall if there is too much air pressure
under the wing.
     Discover how THRUST force is used to overcome DRAG force, caused by 
friction.

Materials needed:

     paper - ditto, 2 sheets per person              markers or crayons
           - 2cm. x 8cm., 1 per person               small box fan
           - newsprint for graph, 1 per team         cool air vaporizer
           - cups, 2 per person                      scissors
           - clips, 5 per team                       cellophane tape
     launcher, wood, with rubber band and thumb tack
     floodlight

Strategy:

     Without any verbal explanation, the teacher will fly a paper airplane four 
times, measureing and recording the data on chalkboard after each flight. (The 
first flight will have 0 paper clips; the second, 1 paper clip; the third, 3 
paper clips; and the fourth, 5 paper clips.)  The teacher will make a graph 
showing the distance of each flight then ask three questions,  "What did you 
see?"  "What was happening?"  "What does the chart show?"  The students will be 
able to read the graph; identify the source of the data; and then label it to 
show "Average horizontal distance". 
     The students will be encouraged to hypothesize the reason some airplanes 
flew straight, others either went to the right or to the left.  (Added weight, 
and uneven folds of the airplane.)

The students will be grouped into teams of not more than four.

Activity 1: The students will make identical airplanes from one sheet of ditto 
paper.  Step 1, fold paper in half, the long side.  Step 2, turn paper over, 
like an open book (spine up).  Step 3, fold upper corners toward center fold.  
Step 4, fold down set of corners toward bottom of paper.  Step 5, repeat Step 3.  
Step 6, fold back along original fold.  Place folded portion on bottom.  Step 7, 
bring one wing portion down to fold, starting at the nose carefully fold down to 
make a wing, repeat for second wing.  (It is important that the creases are even 
and sharp.)  The students will be given an opportunity to test their planes for 
air worthiness.  Following this test flight, they will then make another 
airplane.  Each team member will test their planes to determine the MOST air 
worthy plane to be used in the next activity. 

Activity 2: Teams will repeat the teacher's demonstration, using only ONE plane.  
However, they will fly three trials of each, and record the distance on a data 
sheet.  Using the data, a graph of the "Average distance of each flight,"  will 
be made.  The students will explain their graphs and compare them to the other 
graphs.  (The added weight affects the distance because of GRAVITY, and the 
placement of the clips on the keel of the plane, = center of gravity) 

Activity 3: Each student will hold the end of a 2cm x 8cm piece of paper to 
their mouth and blow over the top of the paper.  (The end of paper rises.)  Now 
blow underneath, what happens?  Measure 3cm from the short end of the paper and 
fold, tape the ends.  Drape the untaped end between the forefingers of each 
hand, now blow over the top.  What happens?  Blow hard across the flat side.   
What happens? 

Activity 4:  Pass out 2 paper cups to each student and a pair of scissors per 
team.  Students should hold the cups about 5cm (2") from their mouth and blow 
between the rims of the two cups.  (The inner cup will pop out.)  Cut out the 
bottom of one of the cups, place it on the bottom of the other cup, and  blow 
again.  The cup will no longer pop out.  (Air pressure is lost through the 
bottom of the cup.) 

Activity 5:  Using a box fan, blow vapor from vaporizer over a wing model to 
show how air travels over the curved and straight surfaces of an airplane wing. 
Students will discuss what they saw.  Repeat the demonstration.  Raise the front 
edge of the wing and repeat the vapor (air) flow demonstration.  Discuss and 
repeat.  For the third demonstration, raise the front edge so that the vapor 
hits the bottom of the wing.  Ask students what would happen if this was an 
airplane?  (Plane would stall and fall).  Using an overhead projector 
transparency with the three wing positions, ask a student to show the path of 
air using arrows.  Is this similar or different from the paper cup? 

Activity 6:  Introduce Bernoulli's Principle.  It takes more energy to move over 
a curved surface, less pressure causes LIFT FORCE.  Gas, steam, water, and other 
liquids are similar to air. 

Activity 7:  Using a model glider placed on a table or desk, ask students to 
hypothesize why the plane isn't moving.  Push it, why isn't it lifting.  What is 
holding it down?  (GRAVITY)  Ask students to explain how Bernoulli's discovery 
applied to counteract the FORCE OF GRAVITY.  Have a student hold a sheet of 
paper in his outstretched hand, then have him run with it.  The paper will LIFT.  
Ask the students to explain how this is applied to the glider. 

Activity 8:  If the glider is pushed it will move and then stop.  Ask students 
to explain how friction causes the glider to stop.  This is called DRAG FORCE. 
How does an airplane overcome DRAG?  What causes an airplane to move?  A 
propeller or jet engine creates THRUST FORCE.  When a plane speeds up, THRUST is 
greater than DRAG.  THRUST is the force that pushes an airplane forward through 
the air. 

     Aerodynamics is the study of air as it moves around objects.  Discuss other 
areas where Bernoulli Principle is applied.  (Automobiles, boats, trains have 
smooth surfaces, reducing friction, this is called "streamlining").  Engineers 
designing skyscrapers, suspension bridges, automobile carburetors, pumps, and 
water driven turbines, all use aerodynamics. 

Performance Assessment:

     Make a diagram of air currents, using arrows to show the direction of the 
air above and below an airplane wing.  Indicate the FORCES involved, and where 
more air pressure, and less air pressure is present. 

     Make a diagram of an airplane.  Show the direction of the four main FORCES 
that affect flight.  Pair the forces.  Describe the balance of forces. 

Rubric:

     5 points - Identification of less air pressure over the curved surface of 
the wing, and more air pressure under the wing.  The direction of the forces of 
GRAVITY, LIFT, THRUST, AND DRAG, are correctly drawn.  GRAVITY vs. LIFT, and 
THRUST vs. DRAG are paired.  A correct description of how LIFT and THRUST balance 
GRAVITY and DRAG as opposing forces.                               

     4 points - Indicates an understanding, but has not described how the forces 
are balanced, or has not identified the air pressure.

     3 points - Has not indicated the correct direction of the forces of 
GRAVITY, LIFT, THRUST, and DRAG, but has described how the forces are balanced. 

     2 points - Has not identified the air pressure.

     1 points - Has not written anything, has only drawn arrows.

REFERENCES:

Model Science Supplement for Magnet Schools and Magnet Programs K-6.  Chicago:
Board of Education,  1991, pp.270-275.
SuperScience Red, v.4, n.6.  New York: Scholastic, March, 1992.
Urquhart, David.  The Airplane and How it Works.  New York: Henry Z. Walck, 1971 
World Book Encyclopedia, v.1.  Chicago: Field Enterprises, 1973.