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