Transcript Slide 1
Bernoulli’s Principle Bernoulli’s Principle • The pressure exerted by a moving stream of fluid is less than the pressure of the surrounding fluid • The faster a fluid moves, the less pressure it exerts Examples of Bernoulli’s Principle • Magic Ping Pong Ball? The reason why the ping pong ball stays in the air is: • The stream of air from the blow dryer is very fast compared to the air in the room. Toward the center the air is moving the fastest, the pressure is lowest. The ping pong ball is pushed up by the high pressure (slow moving air) into the low pressure (fast moving air) right in the center. • Gravity keeps the ball from launching out of the stream and the force of air keeps the ball from falling into the blow dryer. Examples of Bernoulli’s Principle • What happens when you blow air above the top of a sheet of paper? Examples of Bernoulli’s Principle • Try blowing air across the top of a sheet of paper. The paper rises because air passes faster over the top of the sheet and exerts less pressure than the air below it. • The greater pressure from below the paper pushes it up. Application of Bernoulli’s Principle • Bernoulli’s principle partly accounts for the flight of aircraft. • Airplane wings are designed so that the air moves faster over the top of the wings and pressure pushes the wings upward. Application of Bernoulli’s Principle: Shape of the wings • Air passes somewhat faster over the top surface of the wing than beneath the lower surface. • Pressure above the wing is less than pressure below the wing • The wings are shaped so air moves faster over the top of the wings and higher pressure pushes the object upward. Application of Bernoulli’s Principle: Shape of the wings • Air pressure above the wing is …………………….. the pressure below the wing. Application of Bernoulli’s Principle: How does the airplane work? • When an airplane flies it has to overcome weight/Gravity and drag • Because of the lift the plane will rise in the air • This is a result of the Bernoulli’s Principle • Drag is created by air particles and this is overcome by Thrust from engine power. Application of Bernoulli’s Principle: • In high winds, air pressure above a roof can drastically decrease • Air pressure above the roof is less than air pressure inside the building • This produces a lift that may result in the roof being blown off. Bernoulli’s Principle: • Smoke rises up the chimney partly because hot air rises, and partly because it is pushed • Wind blowing on top of the chimney creates a low pressure, the high pressure at the bottom pushes the air up the chimney. The Venturi Effect • It is a special case of Bernoulli’s Principle • It is a reduction in the pressure of a fluid resulting from the speed increase as fluids are forced to flow faster through narrow spaces The Venturi Effect • The reduced air pressure outside the building during strong wind storms has caused the windows to be forced out by the higher pressure inside the building. Explain…Shower curtain • What happens to a bathroom shower curtain when the shower water is turned on full blast? Explain…Shower curtain • Air near the water flows into the lowerpressure stream and is swept downward with the falling water. • Air pressure inside the curtain is thus reduced, and the atmospheric pressure outside pushes the curtain inward Good Luck