Sponsored By Cadette These activities are from the Leader Guide Book, How to Guide Cadettes Through Breathe. Additional activities were developed exclusively by Girl Scouts - Western Oklahoma to correlate with the themes and practices outlined in the Leader Guide and the Girl Guide books. Your STEM Kit in A Box contains the necessary supplies to complete each activity, except where noted. You will use these materials to help the girls earn their Journey badges as Cadettes. These activities MUST be completed as part of their Journey throughout the course of the year. Each kit includes a leader guide that gives background information on the activities. It is recommended that the girls guide themselves through these activities with minimal guidance from you, the leader. Chris Simon, STEM Coordinator Girl Scouts Western Oklahoma csimon@gswestok.org Phone: 405-528-4475 or 1-800-698-0022 This kit is provided through an award from the Oklahoma NSF EPSCoR program and is based on work supported by the National Science Foundation under Grant No. IIA-1301789. Project title: Adapting Socio-ecological Systems to Increased Climate Variability. Any opinions, findings & conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. www.okepscor.org
Sponsored By OK NSF EPSCoR Content Reviewers: Dr. Jody L. Campiche, Assistant Professor of Agricultural Economics and Extension Economist, Oklahoma State University; Dr. Renee McPherson, Associate Professor of Geography and Environmental Sustainability and Girl Scout, University of Oklahoma
Intro Air is pretty pushy stuff. It never pulls or sucks; it only pushes. Right now, air is pushing on you from every direction. This constant push of air is called air pressure. We are so used to air being around us that we don t even notice it. In the 1700 s a Swiss mathematician named Daniel Bernoulli discovered that when flowing air or water changed its speed, its pressure also changed. Today, the girls will learn and use the information they acquire regarding Bernoulli s Principle and apply it to creating a helicopter that can lift more weight than anyone else s. Supplies (for demonstrations): 8 x5 strips of paper (for Wagging Tongue Demonstration) Ping-Pong balls (for Floating Ping Pong Ball and Ping Pong Demonstrations) Bendable straws (for Floating Ping Pong Ball Demonstration) Straight Straws (for Tent with a Straw and Ping Pong Demonstrations) 8.5 x 11 inch pieces of paper (for Paper Tent and Paper, Paper Demonstrations) Supplies (for engineering activity): Box fan Paper clips Paper of various thicknesses: Copy paper Construction paper Card stock Chipboard sheets Plastic straws Fishing line with weight attached Dowel rod w/ hook Tape Background - Principles of Flight Human flight has become a fact of modern life. It is easy to take the physics of flight for granted, as well as the ways in which we exploit them to achieve flight. We often glimpse a plane in the sky with no greater understanding of the principles involved than a caveman. How do these heavy machines take to the air? To answer that question, we have to enter the world of fluid mechanics. Physicists classify both liquids and gases as fluids, based on how they flow. Even though air, water and pancake syrup may seem like very different substances, they all conform to the same set of mathematical relationships. In fact, basic aerodynamic tests are sometimes performed underwater. To put it simply, a salmon essentially flies through the sea, and a pelican swims through the air. The core of the matter is this: Even a clear sky isn't empty. Our atmosphere is a massive fluid layer, and the right application of physics makes it possible for humans to travel it. To achieve flight, you have to exploit the four basic aerodynamic forces: lift, weight, thrust and drag. You can think of them as four arms holding the plane in the air, each pushing, or pulling, from a different direction. First, let's examine thrust and drag. Thrust, whether caused by a propeller or a jet engine, is the aerodynamic force that pushes or pulls the airplane forward through space. The opposing aerodynamic force is drag, or the friction that resists the motion of an object moving through a fluid.
For flight to take place, thrust must be equal to or greater than the drag. If, for any reason, the amount of drag becomes larger than the amount of thrust, the plane will slow down. If the thrust is increased so that it's greater than the drag, the plane will speed up. Every object on Earth has weight, a product of both gravity and mass. Gravity is always pulling down on the mass of the plane. Weight's opposing force is lift, which holds an airplane in the air. This feat is accomplished through the use of a wing, also known as an airfoil. As for the actual mechanics of lift, the force occurs when a moving fluid is deflected by a solid object. The wing splits the airflow in two directions: up and over the wing and down along the underside of the wing. The wing is shaped and tilted so that the air moving over it travels faster than the air moving underneath. When moving air flows over an object and encounters an obstacle (such as a bump or a sudden increase in wing angle), its path narrows and the flow speeds up as all the molecules rush though. Once past the obstacle, the path widens and the flow slows down again. If you've ever pinched a water hose, you've observed this very principle in action. By pinching the hose, you narrow the path of the fluid flow, which speeds up the molecules. Remove the pressure and the water flow returns to its previous state. As air speeds up, its pressure drops. So the faster-moving air travels over the wing exerts less pressure on it than the slower air moving underneath the wing. The result is an upward push of lift. In the field of fluid dynamics, this is known as Bernoulli's principle. What is a Helicopter? A helicopter is a type of aircraft that uses rotating, or spinning, wings to fly. Unlike an airplane or glider, a helicopter has wings that move. How Does A Helicopter Work? Remember, in order to fly, an object must have "lift," a force moving it upward. With an airplane lift is usually created by moving air over the wings. Wings are curved on top and flatter on the bottom. This shape is called an airfoil. That shape makes air flow over the top faster than under the bottom. As the airplane moves through the air, wind starts to move faster over the wing. As a result, there is less air pressure on top of the wing. The increased air pressure below the wing tries to move to this area of low pressure; pushing up and creating lift. A helicopter's rotor blades are wings. A helicopter moves air over its blades by spinning its rotor and creating lift.
Activity SAY: Today we are going to learn about Bernoulli s Principle and you are going to be doing an engineering activity where you have to make a helicopter out of paper that can lift more paper clips than any other groups. ASK: Does anybody here know how an airplane flies? (Allow time for the girls to answer.) SAY: The reason an airplane can take off and fly is because of the curved shape of its wing. This shape is known as an air foil. ASK: Have you ever stuck your hand out the window while your mom or dad were driving? SAY: If you have then you ve experienced Bernoulli s Principle in action. What Daniel Bernoulli discovered years ago, was that when a fluid moves over a curved surface, like the top of your hand, that fluid speeds up. Yes, air is considered a fluid. (Any substance that flows is considered a fluid.) When the fluid speeds up it creates an area of low air pressure. The air that flows underneath the curved surface, the bottom of your hand, moves at the same speed. This creates an area of higher pressure. This high pressure area moves toward the low pressure area which pushes the wing, and your hand, upward, creating lift. Demonstrations The following demonstrations can be done by you the leader, or set up for the girls to participate simultaneously. The purpose of doing these demonstrations is for the girls to understand the effect of air flowing over a curved surface, and to understand the concepts we just learned about Bernoulli s Principle. Wagging Tongue 1. Give each of the girls a strip of paper, approximately 1 inch wide and 6 inches long. 2. Allow the paper tongue to droop just below your bottom lip 3. Blow across the top of the paper. Observe the movement of the tongue. Tent with a Straw 1. Fold an 8 inch X 7 inch piece of paper in half to make a tent. 2. Place the paper tent on a table, or desk. 3. Using a straw, blow under the tent and observe what happens. 4. Blow harder and observe what happens. 5. Try blowing hard against the side of the tent and observe what happens.
Ping Pong 1. Place two ping pong balls on a table about 1 inch apart. 2. Using a straw, blow very hard between the two balls and observe what happens. 3. Did the balls move closer together or farther apart? Paper, Paper 1. Hold two pieces of notebook paper in front of you about 2 inches apart. 2. Blow hard between the papers and observe what happens. 3. Which way did the papers move? Ball and Straw 1. Bend a flexible straw so that the short end is pointing up. 2. Hold a ping pong ball over the opening of the straw and blow. 3. Let go of the ball and observe what happens. 4. What happens if you tilt the straw? (Now, discuss and explain Bernoulli s principle.) Questions for discussion 1. Why does the paper tongue move when you blow gently through the mouth? 2. What happens when you blow harder? 3. Why did the paper table collapse? 4. Why didn t the slips of paper and the ping-pong balls move away from each other? (In all of the demonstrations, the air speed was increased, creating a decrease in pressure. When the air pressure under the tent, between the papers, and between the ping-pong balls was decreased, the air on the other sides had higher pressure. This higher pressure pressed inward, causing the tent to fall to the table, and the pieces of paper, and the ping-pong balls to move closer together.) 5. Now, you describe what is happening with the ping-pong ball and straw. (The fast air moving around the sides of the ball is at a lower pressure than the surrounding, stationary air. If you look closely, you'll see that the ball wobbles while it is levitating in midair. The ball is attempting to leave the area of low pressure, but the higher air pressure surrounding it forces it back into the low pressure area.) 6. Now, based on what was just demonstrated, explain how Bernoulli s principle applies to the lift of a wing on a plane. (Bernoulli s principle applies to the lift of a wing on a plane the same as it does to the paper. Air molecules flow over the curved surface of a wing, creating less pressure on the upper surface than on the lower surface, allowing the wing to lift.)
SAY: Many books state that air speeds up over a wing because it has farther to travel than air moving under the wing. This statement implies that air separates at the front of the wing and must rejoin behind the wing, but this isn t true. Air moving over the top of a wing speeds up so much that it arrives behind the wing sooner than air that travels beneath the wing. Think of pinching a hose. When you place your thumb over the nozzle you pinch off the flow and change its direction. This speeds up the water. When air hits the curve of the wing, it s like pinching it. So, it speeds up. Also, remember that air pushes, it does not pull. Some people believe that the lower pressure above the air foil pulls, or sucks up, the airplane wing and this causes a plane to fly. This is wrong. It is the higher pressure underneath the wing that pushes the plane into the air. ASK: How does this apply to a helicopter? (Allow time for the girls to answer.) SAY: A helicopter is a type of aircraft that uses rotating, or spinning, wings to fly. Unlike an airplane or glider, a helicopter has wings that move. An airplane has to move to create air flow over its wings to give it lift. A helicopter is different in that it moves air over its wings, which are the blades, by spinning them on its rotor and creating lift. SAY: Now, you re going to apply what you ve learned about Bernoulli s Principle and apply it to this engineering activity. In this activity you and a partner are challenged with building a paper helicopter using the template given and making modifications to try to create a design that will lift more paper clips than anyone else s. SAY: You will get to choose from any of the following supplies Paper of various thicknesses: 5. Copy paper 6. Construction paper 7. Card Stock 8. Chipboard sheets Plastic straws Paper Helicopter template Tape (Allow the girls to choose the materials they wish to use to construct their helicopter)
SAY: When constructing your paper helicopter you can use the template as a guide in your design but you will need to improve it. This design as is, will not work. You need to try and improve it. ASK: For instance, do the wings need to be longer, or shorter; do they need to be angled in a certain way; will you need to use heavier paper, or lighter paper? Can you create a design with more than two blades? Do more blades make a difference? Maybe you have an idea of a design. Try it. Regardless of your approach you have (However much time you deem appropriate) minutes to construct your helicopter. The first step is to get your design to spin and lift off. Then after you improve it further you team will try to lift more paper clips than any of the other teams. (After the competition is complete hold a discussion on what design worked the best and why.) ASK: Did longer wings work better than shorter? Why do you think? Did anyone try more blades? How did that work? Did the weight of the paper make a difference? (More propellers make more lift but require more power to turn. Another advantage to more blades is that the rpm can be decreased so the stresses on each blade and root will be a lot lower. Generally, more blades (4 or more) are used for hauling heavy loads at the expense of speed. But also more blades means more cost and more weight. The engine has to be bigger because of the increased number of blades and even though they are turning slower, they will have more induced drag on each blade, so each blade is less efficient. Most helicopter companies would rather use longer and fewer blades to get more lift. It is a lot like comparing a 1000 hp dragster versus a 1000 hp tractor. The dragster has speed but can't do much work, whereas the tractor can do much more work but at a very slow speed. So it goes with helicopters; more blades will result in more lift but slower flight speeds, and high burn rate of fuel due to increased drag. Fewer blades will give the least amount of drag and are therefore more fuel efficient, but are limited on lifting ability and have higher stresses to the blade roots, so they will need to be replaced more often.)