Flight Unit Notes Bernoulli’s principle Aerodynamics

Objectives Describe the relationship between pressure and fluid speed Analyze the roles of lift, thrust, and drag in flight Give examples of Bernoulli’s principle in real-life situations.

Pressure is…… The push or force that particles exert over a certain area. Can be calculated: Pressure = force (N) Area (m2) Units for pressure are N/ m2 or 1 Pa (Pascal)

Pascal’s Principle A change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of that fluid. Blaise Pascal, the 17th century scientist discovered this phenomena. Hydraulic – devices that use liquids to transmit pressure from one place to another. Ex: Brakes on a car – pressure from your foot on the brake pedal is transmitted by the brake fluid to the brake pads which stops the car.

Atmospheric Pressure Pressure caused by the weight of the atmosphere due to gravity. Equivalent to 10 N (1 kg) per square centimeter. Decreases with increase in altitude Less air molecules pressing down on you Ex: Top of Mt. Everest = 33 kPa Philadelphia, Pa (sea level) = 101 kPa Fluids always move form areas of high pressure to areas of low pressure

Buoyant Force is Caused by Differences in Fluid Pressure Fluids are liquids and gasses Pressure increases with depth Pressure on the bottom of objects is greater than the pressure at the top The upward force , caused by differences in pressure , is buoyant force

FLIGHT

Bernoulli’s Principle Swiss physicist and mathematician Daniel Bernoulli developed the theory of moving fluids. The speed of a moving fluid increases, its pressure decreases The moving fluid (air or water) creates a low pressure

Flight-Wing shape The top of the wing is curved As the plane accelerates the Air moves faster over the top than the bottom air. The air that passes over the top of the wing moves faster because it travels a greater distance in the same amount of time The top stream of air creates a low pressure. air that passes under the wing creates a high pressure which creates Lift Lift is created because the air under the wing is slower and exerts higher air pressure. The differences in pressure create lift.

When the plane flies level at constant velocity, all opposite forces of flight are equal: drag = thrust and weight = lift. How the 4 forces of flight interact

Drag Drag opposes thrust. Imagine sticking your hand out the window of a moving car and flying your hand. The force that pushes your hand back is called "drag

Lift Lift opposes weight. Newton's Laws and Bernoulli's Principle generate lift. As a plane goes faster, its lift increases. As a plane moves forward Lift increases.

Thrust Thrust opposes drag. The engine creates thrust and moves the plane forward. (Gravity provides the thrust for a glider.)

Weight Weight opposes lift. Weight and lift are equal when a plane flies level at constant velocity.