MatchCard Science Aerodynamics for Kids
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Objective: Explain how four different forces affect a flying airplane.
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MatchCard Information Pieces define and describe lift, drag, thrust, and gravity. Arrows indicate relation ship between speed and velocity in Bernoulli's Principle..
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This is MatchCard #2 of the Technology Unit Study. Find more information on MatchCard Science below.
Four Aerodynamic Forces
Thrust is the forward motion that pushes that plane forward.
The engine of the plane provides the thrust.
See information below on projects to demonstrate these forces.
Drag is the resistance of the air causing friction on the plane.
The drag will be greater if a plane is flying into wind and less if the wind is blowing in the same direction as it is going.
Gravity pulls objects downward toward the center of the earth.
It creates a downward force on the airplane.
To understand the airpressure that causes the upward lift of the plane, we need to understand Bernoulli's Principle.
It was, in fact, the application of Bernoulli's Principle that finally allowed mankind to take-off into the skies.
An explanation of Bernoulli's Principle is below. Further below on the page you will find 5 demonstrations
of Bernoulli at work.
Bernoulli's Principle states that a fluid substance (including gas or air) will have lower pressure at high speeds, and higher pressure at low speeds.
So how does this help our airplane?
Would air (or anything else) move farther if it was going over a curved surface (like a small hill) or a flat, straight surface surface?
The straight line is the shortest distance and the curved line is the longer distance.
Now if two people started running, one on flat surface and one on a curved hill, and they both started at ended at the same time, who ran the fastest. (The curved surface is larger so that runner ran faster.)
Airplane wings are flat on the underside and curved on the top. When a plane is speeding down the runway before take off, wind is going above and below its wings. The air going above the wing must go faster because it has a further distance to travel because of the curve. If the air is going faster over the wing, will there be higher or lower pressure over the wing. (Less pressure.)
The lower pressure almost causes the plane to get “sucked” up into the sky.
Thrust is what propels the airplane forward. Of course, on an airplane the thrust is coming from the engine, just as the engine propels your car forward.
Here are a few other ways to demonstrate thrust:
- Balloon: Blow it up and let it go. The air pressure escaping propels the balloon forward.
- Paper or styrofoam airplane: What causes the thrust? The force from your hand.
- Rubberband: The stretch in a rubber band propels either the rubberband or a toy that is launched from the rubberband.
- Remote control plane: This is a little more fun and a little closer to the real deal. It just happens to be a little more expensive as well. But like the plane’s engine, the electrical power thrusts the plane forward.
Nothing demonstrates the drag of wind like the wind itself. Fly your paper or styrofoam in the direction the wind is coming from and compare to the direction it is going to.
Think: Airline captains announce to passenger’s their estimated time of arrival once a flight has taken off? Why isn’t the time of arrival the same as that listed on the ticket? Flight time will be longer or shorter depending on wind speed and direction.
Of course the force of gravity is pulling the plane towards the surface of the Earth even as the lift as pulling it upward.
Does gravity act inside an airplane? Yes, if the stewardess drops a cup of water on you it will fall.
Drop two objects one larger and one heavier off a deck or high porch and have them note they hit the ground at the same time. Try it with two objects the same size but different
Would a large plane fall faster than a small plane? No. Gravity causes all objects to fall at the same speed regardless of weight or size. Certain objects (like a feather or parachute) will fall slower because of aerodynamics, not because of gravity.
Hands-On Demonstrations of Bernoulli's Principle
Bernoulli's Toilet Paper Trick
Take a small square of toilet paper and fold it in half. Place it beneath your lips and blow.
: Increased wind speed on top of the toilet paper decreases air pressure on the top and lifts the paper.
Fold a piece of paper in half and make a tent that is open on both ends. Blow through the tent.
: Decreased air pressure inside of the paper tent causes it to collapse on itself.
You will need two empty light-weight plastic drinking bottles. Tie a string around the bottles and let them dangle at the same height.
Altneratives to drinking bottles could include:
- 2 blow up round balloons
- 2 disposable drinking cups
Whichever material you use, you need to tie the two objects to string or yarn and let them dangle.
Blow between the two objects. You can also use a hair dryer to blow between the objects.
Decreased air pressure between the objects causes them to move together.
Place a drinking straw in a cup of water. Blow across the top of the straw.
You will need another observer to watch the affect.
: Decreased air pressure over the straw causes the water to move up the straw slightly.
Really Cool to Do
It is fun to see this principle at work in wind socks or a solar balloon that is open on both sides. You may also make it with a long thin plastic bag (for large trash cans) by carefully cutting open the closed side making the bag open on both ends.
Open up the bag with your arms to decrease the attraction of the inside sides of the bag to the opposite side. Have two or more kids hold the bag on opposite sides.
One person blows into the bag.
: Increased speed of the air inside the bag decreases the pressure inside the bag causing the surrounding air to rush into the bag. The bag fills with much more air than the child has in his or her lungs.
Who Is Mr. Bernoulli?
So who is this Bernoulli character and did he invent airplanes?
Nope, he lived a couple of hundred years before the Wright Brothers. You might want to investigate Daniel Bernoulli before we move on to figure out what his principle has to do with flying.