Bernoulli’s Principle

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Bernoullis Principle

• Created by
• Keith P. Murphy
• Winston Churchill High School
• Potomac, MD

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Bernoullis Principle

• A Swiss scientist born in 1700s that is most
  famous for his work in fluid pressure.

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Remember!!!

• Air is a gas and a fluid
• Air pressure is due to the motion of its
  particles
• ex. The quicker a stream of particles travel,
  the ???????

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Bernoullis Principle

• Pressure in a moving stream exerts less pressure
  than the air surrounding the moving stream

Quick stream low air pressure
Slow stream High air pressure
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Standing Tennis Ball

• In your notes, hypothesize why the tennis ball
  stands in the air.
• Draw the air currents.

Penn
AIR FLOW
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The Answer

• The tennis ball is surrounded by an air stream of
  equal speed, thus equal pressure.
• The down force is G.
• Thus, the ball stands on
• air. The air pressure below
• is equal with the G force.

G
AIR FLOW
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Bernoulli Flight

• Bernoullis Principle is what allows birds and
  planes to fly.
• The secret behind flight is under the wings.

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• The air on top of the wing must travel a longer
• distance than the air below the wing. But, air
  on
• both sides must reach the end of the wing at the
• same time. Therefore, the air on top of the wing
  
• traveling faster less air pressure.

Creates Lift
AIR
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Below is a NASA illustration of what surface
pressure is exerted on what surface areas of the
wing. Is this plane ascending or descending?
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This diagram shows regions of air pressure
around specific areas of the wing. Again, notice
that the low pressure region is above the wing,
allowing for upward thrust.
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LIFT
THRUST
DRAG
GRAVITY
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• The engines provide THRUST.
• The wings provide LIFT.
• Gravity provides the G force.
• And, fluid friction provides the
• DRAG.

• What is happening
• if the airplane is
• flying at constant
• altitude?

What forces are ?