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Discovery Channel Young Scientist Contest
Science Challenges
Activity # 1
Stand up Straight: Your Center of Gravity:
 "Center of Gravity" is a term used by many scientists, especially those involved with the design and construction of airplanes. Every object has a center of gravity, or C of G, including you! C of G is the point around which the mass of an object is equally distributed. It is very important for plane designers to know the exact location of the C of G in order to design a plane that will fly straight and balanced.
Your body has a center of gravity. It is located just behind your navel, or belly button. In order for you to stand upright, your C of G must be supported. To demonstrate this, try this challenge at home.
You will need:
1. A straight wall
2. Yourself
Here's how to do it:
Locate a straight wall with no obstructions or protrusions. Move nearby furniture out of the way. Stand with your right shoulder firmly against the wall. Place the outer edge of your right foot firmly against the wall. Once you are standing against the wall, try lifting your left foot. It's impossible! You'll fall over if you try.
Take your challenge to the next level:
Play a game of one-on-one basketball with a friend. When you are playing defense and trying to keep your opponent from moving around you, watch the motion of his/her stomach. He/she might try to fake you out with wild arm and leg movements, but the center of gravity will always give away his/her intentions. In order for a player to stay balanced, his/her feet must first support the C of G. The direction the C of G is moving is always the direction the entire player is moving.
What's going on?
Why is it easy to stand on one foot when away from the wall, but impossible when standing near it? There are no mysterious magnets under the floor. Observe a standing person. You can see that their center of gravity is positioned over a support base: their two feet. When that person tries to stand on one foot, they instinctively reposition their center of gravity over the remaining foot. Watch yourself in a mirror.
If you really want to find out what's going on, read this:
It is impossible to stand on one foot with a shoulder against the wall. The wall prevents you from positioning your center of gravity over their remaining support foot.
Your navel is almost the exact location of your personal center of gravity. Divers and acrobats curl themselves around their C of G when attempting spins, rolls, and somersaults. Their body naturally tends to rotate around the center of gravity as their body mass is curled around their naval.
Activity #2
25 Cents: An Impossible Balancing Act?
Aeronautical engineers design airplanes around an imaginary line called the centerline. It is a line that travels the length of the plane and through the plane's center of gravity. In this activity, you will locate a centerline of a 25 cent piece (quarter) and you'll learn a fun "science magic" trick to share with your friends.
You will need:
1. Some 3x5 cards, or similar heavy paper
2. Quarters
3. A yard stick
Here's how to do it.
Challenge your friends to balance a quarter on the edge of a card. It's almost impossible, unless you know this scientific trick. Carefully bend the car in a "U" shape, without putting a crease in the card. Place the quarter flat, over the bottom of the "U." Slowly straighten the card. If your hands don't shake, the quarter will balance on the opened card!
Take your challenge to the next level:
Hold you hands waist high in front of your body. Point your index fingers away from you. Place a yardstick on your two index fingers. Position your fingers toward the ends of the yardstick. Slowly slide your two fingers towards each other. They will meet at the center of the yardstick. No matter where they start, they will always meet at the centerline!
What's going on?
As the coin or yardstick leans one direction, friction on that side increases, slowing motion in that direction. The coin tips slightly back and forth, working its way to the exact centerline of the coin, as does the yardstick. Watch the yardstick tip back and forth as you slide your fingers together.
Can you see why knowing the location of an airplane's centerline is so important?
If you really want to find out what's going on, read this:
Orville and Wilbur Wright were not the first people to build an airplane. They are lauded as the first to successfully fabricate and fly an airplane. Many people failed years before the Wrights' successful flight. The problem with early planes was keeping the load balanced over the centerline. Without a method for constantly correcting the load and keeping it balanced over the centerline, the planes tumbled out of control. The Wright Brothers were first to develop a successful method.
The Wrights learned how to warp or slightly twist wing tips to create more or less lift from the wing. The pilot could make slight adjustments to keep the plane flying level without worrying about slight shifts in weight around the centerline.
Activity 3:
Understanding Lift: No matter how hard you blow, it won't go.
How a simple curved surface on an airplane wing can create enough lift for flight is an amazing scientific feat. Here is a simple trick designed to demonstrate how a small amount of moving air can create a large amount of lift.
What you'll need:
1. Large rubber stopper with one hole, or empty thread spool
2. 3x5 cards or old playing card
3. Thumb tack
4. Ping pong ball
5. A Funnel
Here's how to do it.
Cut a 3" x 3" piece of card stock or heavy paper. Push a thumbtack through the center of the card. Insert the point of the thumbtack into the hole in the stopper or spool. Hold the card in place while you begin to blow through the hole on the other side of the stopper. While you are blowing, release the card. It stays in place until you stop blowing!
Take your challenge to the next level:
Tip your head back and try blowing through a funnel to expel a ping pong ball. It's amazing! Although it looks simple, it's just about impossible for a human to blow a ping pong ball out of a funnel.
How can that be? Surely your breath is sufficient to move the light ball?
What's going on?
Gravity is pulling down on the card, but it stays in place as long as air is running over its upper surface, just as a wing lifts the plane. The stream of air blown through the spool impacts the card and is deflected over the surface of the card. The rushing air does not push down on the surface of the card as much as the air underneath the card. Atmospheric air pressure holds the card against the stopper.
The thumb tack serves the purpose of centering the card on the stopper. With practice, you can eliminate the thumb tack.
The same phenomenon occurs in the funnel, but even with more amazing results. The cone shape of the funnel directs moving air not only across the bottom of the ball, but up the sides as well, creating an even greater area of low pressure.
If you really want to find out what's going on, read this:
We live in an atmosphere that is approximately 60 miles thick. Although air doesn't feel very heavy, it does have mass and therefore weight in the earth's gravity field. The weight of air exerts almost 15 pounds of pressure on every square inch of everything in the atmosphere, including you!
A 3" x 3" card has about 135 pounds of pressure pushing down on the top surface, and the same amount pushing up on the bottom. When you blow across the top surface, you are lowering the pressure a little, allowing the pressure underneath to hold it up.
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