Name ______
Air and Aerodynamics – A Review
1. Air is invisible and not very dense yet it is made of matter and therefore must take up space. How could you prove to someone that air does indeed take up space? Give two examples.
a. You could take a bag and wave it in the air until it fills the bag. Then tie off the end and you will see that air takes up space.
b. You could put a tissue into the bottom of a cup. Then tip the cup upside down and press it down into a sink full of water. When you take it out of the water and remove the tissue it will still be dry because the water could not enter the cup because it was full of air.
2. Air is a fluid, just as water is. When you go deep under the water you can feel the pressure of the water. How can you show that air exerts pressure?
When you pump air into a bicycle tire, the tire will fill up and you will be unable to put any more air into the tire because of the pressure that the air exerts.
3. Air is a fluid and is capable of being compressed. This fact can be used in many useful ways. Describe two things that use compressed air.
Any two of the following: Scuba tanks, pneumatic tools, paint sprayer, insecticide sprayer, submarine ballast, filling a tire, aerosol cans, etc.
4. Billy bought his girlfriend a bunch of balloons for her birthday on January 15. It was a very cold day, -37 degrees. As he took the balloons from the store to the outside they shrunk and looked really wimpy. “What a rip-off,” thought Billy. What happened to the balloons?
The air in the balloons cooled when Billy went outside. The cooler air contracted and so the balloons shrunk.
What will happen when Billy takes the balloons back inside? Why?
When Billy goes back inside, the air inside the balloons will heat up. This will cause the air to expand. The balloon will probably not fill completely up again though.
5. Daniel Bernoulli discovered something very interesting one day. His discovery became known as Bernoulli’s Principle. What is Bernoulli’s Principle?
Bernoulli’s Principle states that as the speed of a fluid increases, the pressure decreases.
6. Bernoulli’s Principle can be demonstrated in a number of ways. Describe two.
a. When air flows over an airfoil, the air must move faster across the top of the camber and that causes the air pressure to decrease. The air under the wing will try to move up into the area of low pressure and will force the wing up. This is how a wing creates lift.
b. If you place two pop cans on a table and then blow between the cans, the cans will move together because the moving air blowing between the cans will cause the air pressure between the cans to decrease. The higher-pressure air will try to move into the area of low pressure and will push the cans together.
7. Everything in the universe has a gravitational pull, you and your pencil included. Why doesn’t your pen stick to you like we stick to the earth?
The size of the Earth compared to the size of a person is many thousands times greater. Therefore the gravitational pull of the Earth is much greater than that of a person. Because of this, the pen is pulled to the floor by the Earth’s gravitational pull.
8. There are four forces that affect flight. Draw a diagram of an airplane in flight and label the forces acting upon it. (Label the positive forces green and the negative forces red) hint: positive forces help the plane stay in flight, negative forces don’t
9. How does the design of an airplane increase the positive forces and decrease the negative forces of flight?
Positive:
a. The camber of the wing is designed to create lift. Flaps and elevators are designed to increase the camber and provide more lift.
b. The propeller and jet engines provide thrust.
Negative:
a. To minimize the effects of gravity, airplanes are built with as light of materials as possible.
b. To minimize the effects of drag, planes are streamlined and landing gear folds up into the plane.
10. How does a bird’s structure and actions increase the positive and decrease the negative forces of flight?
______
11. How does a flying squirrel “fly”?
A flying squirrel does not really fly. It glides. A flying squirrel has flaps of skin, which catch the air in them, and allow the squirrel to glide from tree to tree. They can not take off from the ground and fly upwards.
12. How does a big fat bumble bee manage to fly?
______
13. What is Newton’s third law of motion?
For every action, there is an equal and opposite reaction.
14. What does Newton’s third law of motion have to do with the flight of a jet airplane and with the flight of a rocket? Draw diagrams to help explain.
Newton’s third law states that “for every action, there is an equal and opposite reaction. This means that in the case of a rocket, as the fuel burns and shoots out the bottom of the rocket, the reaction is that the rocket moves forward. The same is true of the jet engines. As the gas shoots out the back of the engine, the plane moves forward. (opposite direction).
15. What are five properties of air we discussed in class?
a. Air is mater – it is made up of atoms and molecules
b. Air takes up space.
c. Air has mass.
d. Air can be compressed.
e. Air is a fluid and a gas.
16. What gases make up the air around us? Give percentages.
78% nitrogen, 21% oxygen, 1% carbon dioxide and other gases
17. Bobby-Jo was worried that her old wagon was going to rust. Her mother recommended a new coat of paint. Why would this help Bobby-Jo’s wagon?
The coat of paint would protect the metal from moisture and oxygen in the air, (both of which are needed to cause rusting.)
18. Goldpan Girdy and Lucky-Strike Sam were caught in a cave-in at their small gold mine. The little tunnel was sealed tight and it was cold and dark. Sam suggested they light their lanterns so they could look around and maybe find a way to help those outside who were frantically working to dig them out. Girdy said, “No! Don’t light the lanterns; we may be here for awhile.” In their situation, why was Girdy’s decision the best one?
Because oxygen is necessary for combustion, lighting the lanterns would be a bad idea. The fire would burn up the oxygen in the air, leaving nothing for Girdy and Sam to breathe.