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Lesson Plan – The physics of Flight

The Physics of Flight
Outreach Program Lesson Plan

*This lesson plan is intended for use by WAAW Foundation Instructors (Fellows), as well as individual classroom teachers.  WAAW Foundation curriculum may not be reproduced or distributed without written permission.  If you wish to copy parts or all of this document, please contact frances@waawfoundation.org.

Class Description-

In this class, students will explore the forces involved in flight through several demonstrations and experiments.  They will work to design their own gliders in groups and participate in the design process.

Total class time: 90 minutes

Class Outcomes-

-Students will be able to identify and explain the four basic principles of flight: Weight, drag, lift, and thrust.

-Students will be able to describe the Bernoulli Effect and its role in generating lift.

-Students will understand the basics of the design process, and will use that process to create a basic paper glider.

Materials List-

The kit to teach this class should include:
-Drinking Straws
-Balloons (standard latex)
-String
-Ping-Pong balls or empty soda cans
-Copy paper
-Paper clips
-Scotch (Clear) Tape
-Masking Tape or Chalk

Pre-Class Preparation and Set-Up

Before teaching this class, try out the activities and demonstrations yourself, so that you know what to expect for timing and findings when you do them with students.  Gather materials, and print out paper airplane instructions and templates from www.funpaperairplanes.com.  Do an internet search, and print some pictures of different flyers to use at the beginning of class (airplanes, gliders, helicopters, kites, birds, bugs, etc.)  Or, if you will have access to a computer and projector with your students, put together a quick slideshow of pictures.

Depending on your classroom space and set-up, you may want to set up the airfoil floor diagram (from the “Lift!” section) before class starts.   Set up chairs and tables to provide group work space.

Introduction (5 minutes)

Who has watched something fly before?  Whether it was a plane or helicopter, a bird or a bug, we’ve all seen something fly.  Has anyone ever imagined themselves flying?  Humans have always been fascinated by flight, and although we may not be able to fly as perfectly as a bird, we have developed ways to get airborne.  Have students take a look at pictures of different flyers (either printed out before class, or on a projector.)  What things do they have in common?  How are they different?  How do they compare to flyers we find in nature?

Flight ForcesToday we will be Aerospace Engineers!  We will be looking at airplanes and gliders, and the forces involved in flight.  There are four forces that act on an airplane as it flies, and they are:  Thrust, lift, drag, and weight.  (Draw a simple diagram on the board to illustrate these concepts.)  Weight of course is the force of gravity acting on the mass of the plane.  Drag is the force of the air pushing back on the plane as it moves forwards.  The other two forces (lift and thrust) are what we are going to explore next.

 

 

 

Lift! (20 minutes)

It seems almost impossible that something as large and heavy as an airplane can stay up in the air, or even get off the ground in the first place.  The secret to this is LIFT.  We’re going to do a couple of little experiments to see how this works.

Divide your students into groups of 3 or 4, and give each group two ping-pong balls, two pieces of string (each about 1 foot long), some tape, and a drinking straw.  Have the students tape a ping-pong ball to each piece of string, and then dangle the two balls about 2 or 3 cm apart from each other.  Attach the ends of the string to something solid, like a table (the ping-pong balls need to be dangling in open air- it will not work if they are up next to a wall.)  Tell the students that they are going to use the straw to blow air between the ping-pong balls.  Ask each group to record- what do they think will happen?  Most will probably say that the ping-pong balls will be blown away from each other.  Have the students try the experiment.  What happened?  The ping-pong balls should have moved closer to each other, maybe they even hit each other!  Why?  What’s going on here? (If the ping-pong balls do not come towards each other, they are probably hanging too far apart.  Have students reposition them closer together.)

(This same experiment can be done using two soda or juice cans instead of ping-pong balls, if these are more available.  Just lay the cans on a flat surface and use the straw to blow between them.  The cans should roll together in the same way the ping-pong balls come together.)

Bring the class together for an explanation:  We just witnessed something called the Bernoulli Effect taking place.  Fast moving air creates low-pressure.  The faster air moves, the lower the air pressure will be.  When you blow between the two ping-pong balls (or cans) you create a pocket of low pressure between them.  The higher pressure on the outside presses in on the ping-pong balls, and they come together.  (Consider using a diagram, like the one below, to illustrate this to your students.)Bernoulli

 

This Bernoulli Effect is used to keep airplanes up in the air, and we’re going to do another demonstration to see how this works.  Using masking tape on the floor, or chalk if you are outside on pavement, outline the cross-section of an airplane wing (which is called an airfoil.)  It should be curved on the top, and flat on the bottom.  Now, create airflow lines that come towards the airfoil, and then separate to go above and below the airfoil, then come back together after they have passed the wing.

Airfoil1

Once the picture is complete, make sure students understand what they are looking at, and which side of the airfoil is the top of the wing.  To demonstrate how this works, your students will represent the air.  In pairs, they should walk towards the airfoil at a slow pace.  Have one pair of students demonstrate.  Once they reach the airfoil, they get separated, and some of our air must go above the airfoil, and some below.  Now, because there is no offset of the air, these two particles must reach the back of the airfoil at the same time.  What does the air going over the airfoil (along the curve) need to do in order for this to happen?  It needs to move faster.  Have a few pairs walk through the demonstration so everyone sees.  Now, if the air on top of the wing is moving faster, what does that mean? (Think about the last experiment we did…)  It means that there is lower pressure above the wing!  The slower moving air below the wing will be at a higher pressure, and will push the wing up.  We call this force LIFT and it keeps our airplanes up!  The Bernoulli Effect strikes again!

Airfoil

Thrust! (10 minutes)

Now, in order to get this lift, we need to have some relative air movement.  This may come from wind, but most aircraft need THRUST to get the air moving around the wings.  This next demonstration will show us how thrust moves an aircraft.

Get students back into their groups once again.  Give each group a drinking straw, a balloon, a long piece of string (at least 2 meters) and some tape.  One student should blow up the balloon, but don’t tie it!  Have the student hold it closed (or use a paper clip to prevent air from escaping.)  Another student should tape the drinking straw to the balloon so that it is lined up from top to bottom with the Balloon Thrustballoon.  Then, have the students put the string through the straw.  Have two students each take an end of the string, and hold it tight, horizontally.  Now, slide the balloon to the end of the string and you’re set for take-off!  Before they let go, have students make predictions.  What will happen to our airplane (the balloon)?  Why?  When groups have made their predictions, they can release their balloon and let it fly!  If nothing is obstructing its path, the balloon should zoom down the length of the string to the other end.

So what is happening here?  We are seeing Newton’s Third Law of Motion: For every action there is an equal and opposite reaction.  As air is forced out the end of the balloon, it exerts an equal and opposite force, which pushes the balloon down the string.

This activity most closely demonstrates jet propulsion, but there are other forms of propulsion that can be used.  Can you think of any?

If you have time, you can also use this activity to explain more about drag:  Drag is the force from the air in front of the balloon as it makes it’s way down the string.  The air has mass, and wants to stay at rest.  As the balloon pushes on the air in front of it, the air pushes back, which creates drag and slows the balloon down.

The Glider Challenge (40 minutes)

Not all aircraft use continual thrust.  Some aircraft have an initial thrust and/or use gravity to create relative airflow and generate lift.  These aircraft are called gliders.

We are going to create our own gliders out of paper!  In the appendix you will find instructions and templates from www.funpaperairplanes.com.  (These are commonly called paper airplanes, although they are really gliders because they do not use thrust once released from your hand.)  Each group can choose a design, and follow the instructions to create a glider.  Then, give them some initial thrust (throw them) and let them fly!

Now that everyone has their basic glider, we are going to try to make them better.  Help the students to brainstorm things that might make their gliders go farther or travel more accurately.  Things to try:

  • Add weights to your glider- Using paperclips on the glider may help it balance and produce more steady flight.  Try putting weight in different places and see what happens.
  • Create fins or tips- The vertical fins or tips can help guide airflow and keep your glider more stable.
  • Adjust the length of the glider, wing angle, width, etc.
  • Cut flaps in the wings or tail of your glider- They will act similarly to fins or tips.
  • Try a different glider design- follow the instructions, or create your own!

Before they go to try these things out, ask your students- How will you be able to tell if your current glider is better or worse than the last one you tried?  Help students develop criteria (distance, accuracy, repeatability, speed, etc.) that they can record in notebooks or on paper that will help them judge their gliders.

Give students plenty of time to adjust their gliders, and try out new things.

If students have trouble getting creative with their glider, have them take a look back at the pictures from the beginning of class, and ask them to think about the types of things they see on real airplanes, or on  birds (for instance, a tail.)   Is there any way they can replicate that element with paper and tape?

Conclusion (15 minutes)

At the end of class, gather your students back together to discuss what they did, and the process they went through to design their gliders.  Ask some questions to get conversation started:

  • What was your best design?  What elements did it have that made it work?
  • Did your group experiment with adding weight, fins, or flaps?  What difference did these things make?  Did placement of these things make a difference?
  • No matter how great your glider was, eventually it would fall back to earth.  Why are airplanes able to stay airborne so much longer than gliders?
  • How do you think the process you went through compares to what real engineers would do when designing a glider?  What would be the same?  What would be different?  While it may become more complicated for engineers, the design process that they use has the same components as the process that you used in class today.
  • Aerospace Engineers are the people who design aircraft in real life- What do you think might be some exciting parts of that job, and what might be some challenges?

References-

Paper Airplane Instructions and Templates from:
http://www.funpaperairplanes.com/plane_downloads.html