|
Contributed By: Oregon Museum of Science and Industry
|
| Share This Experiment |
Experiment Category:
Objective:
Learn about the Bernoulli effect by building an airfoil (airplane wing) and making it fly.
What You Need:
- Regular weight copy paper
- 5" x 10" corrugated cardboard
- Ruler
- Bamboo skewers (shish kebab sticks, available in grocery stores) or knitting needles
- Clear tape
- Scissors
- Pencil
- Small electric fan
- Cardboard, cardstock, manila file folder or heavy weight paper 4"x 6" or larger
- Pencil-top (cap) erasers
To Do and Observe:
1. Build a base to use as wing testers. a. With a 5"x10" piece of corrugated cardboard, make a fold at 2", 4" and 6" from the end. b. Fold the cardboard into a box-like structure with open ends shaped like a trapezoid with the widest edge on the bottom. c. Tape the structure together into this shape. d. Make two dots 3 inches apart in the center of the top of the cardboard base. e. Poke the rods (skewers or knitting needles) through the top of the base at the dots. Make sure that the rods are straight with the ends secured in the bottom of the base to keep them stationary. f. Place the pencil-top erasers on the sharp ends of the skewers or knitting needles for safety.2. Make your wing a. Draw a line across a sheet of 8.5" x 11" paper, 6" down from the top (so you have two unequal parts--one 6" x 8.5" and one 5" x 8.5"). b. Make a light fold along the line--do not crease heavily. c. Bring the corners of the paper together, causing the longer side to arch. Tape the ends of the paper together. The wing should have a gentle curve on the upper surface. d. Line up your wing over the rods on your base and mark where the rods on should poke through. With the pencil, poke holes through the paper both the upper and lower sides of the wing--the holes should be big enough for the yellow part of the pencil to fit through.3. Set up your fan on the table.4. Anchor your base in front of the fan (you can tape it or hold down the bottom with a book).5. Remove the erasers, and slide the wing all the way down the rods to the cardboard base.Replace the erasers. The wing should be curved on the top and flat on the bottom. You may choose to experiment with different positions.6. Turn on the fan and observe the wing for 15--90 seconds. Record your observations.7. This time, when the wing is halfway up the rods, hold a card in front of the wing to block the wind from the upper surface. If the lift is coming from lower pressure on top of the wing, blocking the wind will cause the wing to slide down to the base. Try to block the wind in different ways. Observe for 15--90 seconds. Write down your observations.
What's Going On:
The shape of an airplane wing helps create the force necessary to lift an airplane into the air. Airplane wings are specially designed to provide the upward force called lift. Air molecules travel farther over the long top of the wing. Since the air molecules on the top surface of the wing have to go farther in the same amount of time, they are moving faster than the air molecules on the lower wing surface. When the molecules move faster over a greater distance, they are more spread out (less dense). When molecules move, they put pressure on whatever they strike. The more molecules that strike the object, the more pressure or force there is on the object. Because there are more air molecules per inch along the bottom of the wing, the pressure of the molecules hitting the bottom of the wing is greater than the pressure from the less dense layer of molecules on the top surface of the wing. This pressure difference causes the wing to be pushed or lifted upward. Daniel Bernoulli developed the physical principle that describes these phenomena in 1783. He discovered that increasing the velocity of a gas (or liquid) would lower its pressure. Thus, most airplane wings are designed to take advantage of air pressure differences.
Parent/Teacher Tips:
Create a little competition! Mark off the rods in half-inches (or centimeters). Make a couple of wings and record the height to which each wing rises. Calculate the average (or mean) of your trials. Or investigate the structure of the wings of birds. How does the size and shape of the wing affect the bird’s flying habits? For example, compare an eagle, albatross, chicken, robin, duck, penguin and emu. What is the wing shape? What is the overall body size and shape? What is the wingspan? Do they flap or soar? How long can they soar?