Fluids and Motion 3.3

Daniel Bernoulli Discovered as the speed of a moving fluid increases, the pressure decreases. Called the Bernoulli Principle.

The water is moving faster than air, so the pressure is decreases. The higher air pressure pushes the ball into the water.

Look at the Boeing 737. It weighs 350,000 N. How can it fly? Bernoulli’s principle: The fast moving air above the wing creates lower pressure than below the wing. Air under the plane actually helps lift it up.

Thrust and Lift Lift is created by the wing and speed of air around the wing. Speed of the plane is mostly due to thrust, which equals the forward force produced by the engines. When thrust is GREATER, the speed of air across the wing is GREATER, which in turn increases LIFT!!

Wing Size, Speed and Lift Lift depends partly on wing size Small wing will need a large thrust. Small wings keep the weight of the plane down, which means it can have a greater speed. Large wings because there is no engine. Requires air currents to fly

Bernoulli and Birds Birds have no engine –Must flap their wings to push through the air Small Birds have a high flap rate Large Birds=large wing=more lift.

How can a baseball pitcher take advantage of the Bernoulli principle?

Drag Drag is a force parallel to the velocity of the flow –SOO…the force opposes or restricts motion in a fluid Turbulence –An irregular or unpredictable flow of fluids Lift is often reduced when turbulence causes drag!

What is Drag? How does it relate to turbulence? How do high speed air craft overcome this problem?

Pascal’s Principle States that a change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of that fluid Hydraulic devices use Pascal’s principle to move or lift objects

What is the Pascal principle? Explain what types of systems use this principle. Use examples.

Page 83; 3,4,6,7 &9