THE SKY’S THE LIMIT GRADE SIX SCIENCE

LESSON ONE A flying object needs to generate two forces acting in different directions: An upward lift to overcome the pull of gravity (lifting) A strong forward thrust to push the object forward (propelling) Living things that fly differ from aircraft in that their wings have to perform both of those tasks (lifting and propelling). Force: a push or pull that makes an object move if it is stationary or change speed or direction if it is already moving.

LESSON 2 Balanced forces: forces that do not produce motion when they interact. For example, when you sit in a chair, gravity pulls you toward the Earth. At the same time, the chair pushes you upward, away from the Earth. The force of the chair cancels out the force of gravity and you remain motionless. Unbalanced forces: forces applied at the same time that produce acceleration when they interact. For example, when two people push a stalled car forward, the combined forces they apply overcome the friction between the road and the tires. When a steady speed is reached, the forces are balanced and there is no further acceleration. Gravity: the force that attracts things toward the center of large objects. Earth’s gravity causes people and objects to have weight.

LESSON 2 CON’T Acceleration: the rate of change of an object’s speed with time. To speed up, an object must accelerate; to slow down, it decelerates. Air Pressure: the amount of force air exerts on an object in motion. Mass: the amount of matter in an object. An object’s mass stays the same everywhere, but its weight will change in space or anywhere the force of gravity changes. Weight: how heavy the force of gravity makes the mass of an object.

LESSON 2 CON’T Properties of Air: Air exerts pressure Air takes up space Air has mass and weight Hot air rises and expands Air can be compressed Air resist things moving through it Air has an insulating quality

LESSON 4 Compress: squeeze together to make smaller or more compact. Current: a flow or a stream of water or air moving in one direction Fluid: any substance that flows easily, including both liquids and solids. Air is fluid. Perpendicular: at right angles to a given surface. Resistance: an opposing force Rudder: a hinged piece attached at the rear of a boat or aircraft, used for steering. Turbulence: irregular movement of fluid

LESSON 4 CON’T Air and water are very similar. Air is actually a fluid and demonstrates the effects of resistances and compression. A fluid is any substance that flows easily. Liquids and gases are both fluids. All fluids resist the motion of objects travelling through them because those objects rub against the atoms and molecules that make up the fluid. The faster objects move the more resistance they meet. Air pushes harder against a racing cyclist as the speed of the racer increases. Since air resistance generates heat, high-speed aircraft must be made of materials that can withstand intense heat. Since air is a fluid, like water, air speeds up as it moves around an object or through a narrow channel.

LESSON 5 Lift: The aerodynamic force that acts perpendicular (at right angles) to the direction of motion, causing an object to rise. Bernoulli’s Principle: If the speed of a moving fluid increases, the pressure it exerts decreases. In other words, fast moving fluids exert less pressure than slow moving fluids.

LESSON 6 Airfoil: a streamline shape, usually with a rounded leading edge and a sharp trailing edge, as in the cross-section of a wing or propeller blade. Drag: the aerodynamic force that acts against an object moving though air or another fluid. When you swim, you are slowed down by the drag of the water. Aerodynamics: the science that deals with the flow of air around an object in motion.

QUESTIONS YOU SHOULD KNOW (LESSONS 1-6) What are the properties of air? What would happen to an airplane on the runway if gravity and lift were balanced? Explain why? Explain how the shape of an airplane wing helps an airplane get off of the ground and stay in the air. What is Bernoulli’s Principle and how does it explain what happens when you blow air between two balloons dangling side by side?

LESSON 7 The four forces that act on an airplane are lift, drag, thrust and weight. Thrust: the force that pushes a flying object forward. Drag: opposite of thrust; slows an airplane down. Lift: the force that pushes flying objects in an upward direction, allowing them to fly. Weight: opposite of lift; the force that pulls flying objects down. Lift and thrust must be greater than weight and drag for an airplane to fly.

LESSON 7 CON’T Propulsion: a driving force that pushes an object. In jet propulsion, hot gases forced out of the back of an aircraft, rocket or boat push the aircraft forward.

LESSON 8: Although a wing and a propeller are both airfoil shapes, they perform two different jobs. The wind provides lift and the propeller provides thrust. Propeller: a device consisting of a revolving hub with blades that propels air or watercraft. Rotate: turn in a circle or revolve, around a centre or axis. Rotor: a system of rotating blades that enables a helicopter to fly.

LESSON 9 Kites and hang-gliders make use of the same aerodynamic forces. Remember, aerodynamics deals with the flow of air around an object in motion. Kites and hang-gliders overcome the force of gravity and are kept in the air by the lift forces of wind and pressure. The shape of an object affects the amount of drag it produces. A streamlined shape produces little drag. Streamlining is important in airplanes as well as cars, trains, etc. Streamlined machines use less power because their design is sleek and trim allowing it to move through the air easily and smooth.

LESSON 9 Aerodynamic: having to do with the motion of air and the forces that act on objects moving through the air. Computer simulation: a model or test developed on the computer that has the characteristics and actions of the real object or test. Gliding flight: flying using only the forces of air True flight: flying using energy or power. Streamlining: shaping an object to offer as little resistance as possible for movement through fluids. Wind tunnel: A tunnel-like chamber where artificial wings permit testing of the effects of air pressures on objects

LESSON 10 **You were given a sheet called “Characteristics of Flight: Parts of Plane”. Please be able to identify and define the parts of a plane. (ie. Label a diagram; fill in the blank for definitions) Control surfaces: the rudder, ailerons and elevator, which work together to control the direction of an airplane. Control surfaces change the airflow around the surfaces of an aircraft.

LESSON 11 Efficiency: the ability to do something without wasting resources such as time, energy, money, etc. Jointed: consisting of two parts that are joined together ina way that allows the parts to move in different directions. Birds, insects and bats are nature’s only true fliers. Birds launch themselves using their leg muscles and then use their wings to get lift and thrust. Some birds fly mainly by flapping; others combine flapping with gliding or soaring. Gliding birds keep their wings extended and coast downward, using almost no energy. Soaring birds use air movement (wind) to propel themselves without flapping their wings.

LESSON 11 CON’T Insect wings vibrate at astonishing speeds and while they may look fragile they are amazingly strong. Many plants use gliding flight to distribute their seeds. Some seeds float, some glide and some spin. Bats are the only mammals that can truly fly. Others (ex. Flying squirrel) use special body adaptations to help them glide long distances.

QUESTIONS YOU SHOULD BE ABLE TO ANSWER (LESSONS 7-11) 1.What are the four forces that act on an airplane and which are required for flight? 2.What is the difference between a wing and a propeller. 3.What is streamlining and why is it useful? 4.What are wind tunnels and why are they useful? 5.How is flight in nature different than man-made flight?