Section 3-3

Fluid Speed and Pressure Bernoulli’s Principle: As the speed of a fluid increases, the fluid’s pressure decreases. Bernoulli’s Principle: As the speed of a fluid increases, the fluid’s pressure decreases. –Example: Blowing air through two pieces of paper causes less pressure between the paper than on the outside. The pressure outside will push the paper together.

Factors that Affect Flight Lift:an upward force on an object that moves in a fluid Wing design and lift: Wing’s are shaped so the air above the wing moves faster than below the wing. Since there is more pressure under the wing, it pushes up on the wing (lift). wing. Since there is more pressure under the wing, it pushes up on the wing (lift). Thrust:a forward force produced by a plane’s engine

How does thrust affect lift? If a plane is moving faster (more thrust) than the air moves faster over the wing and will create more lift. How does thrust affect lift? If a plane is moving faster (more thrust) than the air moves faster over the wing and will create more lift. Wing size, Speed and Lift: Planes with small wings need an engine to create lift. A plane with a larger wing (such as a glider) doesn’t need an engine since a lot of lift is created from the large wings. Wing size, Speed and Lift: Planes with small wings need an engine to create lift. A plane with a larger wing (such as a glider) doesn’t need an engine since a lot of lift is created from the large wings.

Bernoulli and birds:Instead of engines, birds flap their wings. Birds with small wings must flap often but birds with larger wings can flap less. Bernoulli and birds:Instead of engines, birds flap their wings. Birds with small wings must flap often but birds with larger wings can flap less. Bernoulli and baseball: Curve balls move in the direction of less pressure because the air speed is not the same on both sides. Bernoulli and baseball: Curve balls move in the direction of less pressure because the air speed is not the same on both sides.

Drag and Motion in Fluids Drag:a force that opposes the motion in a fluid (similar to friction) How does turbulence affect drag? Turbulence (change in pressure or air speed) causes drag.

Pascal’s Principle: a change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of the fluid Pascal’s Principle: a change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of the fluid Hydraulics: devices that use Pascal’s principle (fluid pressure) to move or lift objects Hydraulics: devices that use Pascal’s principle (fluid pressure) to move or lift objects –Example: To make a car stop, the driver pushes on the brake pedal, which puts pressure on a liquid. The liquid makes the brake pads press against all of the wheels equally to stop the car.