Download - Fluids & Motion Ch7.3 8th
Chapter 7 Section 3
Objectives: Describe the relationship between pressure
and fluid speed
Analyze the roles of lift, thrust, and wing size in flight
Describe drag, and explain how it affects lift
Explain Pascal’s principle
Fluid Speed & Pressure:Property of moving fluids- Bernoulli’s Principle
As the speed of a moving fluid increases, the fluid’s pressure decreases
Ex: try the two sheets of paper demoEx: table tennis ball in a stream of water
http://pilotsweb.com/principle/art/venturi01.jpg
Factors That Affect Flight:Bernoulli: fast moving air above the wing exerts
less pressure than slow moving air below the wing; the greater pressure below the wind exerts an upward force [Lift] – wing shape is the key!
Lift pushes the wings upward against the downward pull of gravity
http://www.hiflykites.co.za/kite-online-shop/x-zylo-flying-principles-3.gif
Thrust & Lift:Amount of lift is determined by the speed of
the air traveling around the wing
Speed is determined by thrust
Thrust: the forward force produced by a plan’e’s engine
http://www.yesmag.ca/focus/flight/bernoulli.gif
http://library.thinkquest.org/2819/graphics/forces.jpg
Wing Size, Speed, and LiftLift depends on wing size
Jet create a large amount of lift with small wings because it has a strong thrust
Glider has large wings to create lift, no engine, no thrust,
Bernoulli & Birds:Birds flap wings because they have no engines
Small birds flap at a fast rate, large birds flap slowly
Bernoulli & Baseball:
Throwing a screwball or curveball that is difficult to hit
http://library.thinkquest.org/C005776F/images/curveball.jpg
http://www.lokeshdhakar.com/images/2007/baseball_pitches/screwball.png
Drag & Motion in Fluids:
Drag: the force that opposes or restricts motion in a fluid
Ex: walking in a strong wind
Caused by an irregular flow of air “turbulence”
Turbulence & Lift:
Lift is reduced when turbulence causes drag
Planes have flaps to reduce turbulence
Flaps change the shape or area of the wing, reducing drag and increasing lift
http://virtualskies.arc.nasa.gov/aeronautics/tutorial/images/FlapsAilerons.gif
Pascal’s Principle:A fluid in equilibrium contained in a vessel exerts
a pressure of equal intensity in all directions
A change in pressure at any point in an enclosed fluid will be transmitted equally in all parts of that fluid
http://panda.unm.edu/Courses/Price/Phys160/F33-3.jpeg
Pascal’s Principle & Motion:
Hydraulic devices use Pascal’s principle to move of lift objects
Hydraulic devices can multiply forces (use liquids)
Ex: car brakes
Quick Quiz:
What forces act on an aircraft?
When an airplane is flying, does the air pressure above a wing compare with that below the wing?
How is thrust related to the speed of an airplane?