1) As the velocity of a fluid increases, the pressure of the fluid decreases. 2) Bernoulli's principle states that a region of fast-moving fluid has lower pressure than a region of slower-moving or stationary fluid. 3) Many common devices and phenomena rely on Bernoulli's principle, including aircraft wings, venturi tubes, and spray bottles.

1. In a steady flow of a fluid, the pressure of the fluid
decreases when the velocity of the fluid
increases.
Fluid consist of liquid or gas

3. Demo: Blow It Up
Hold a sheet of paper in front of your mouth and blow;
the paper will rise.
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4. Observation Explanation
As air is blown across the top of a piece
of paper, air flows at high speed and this
creates a region of low pressure across
the top of the paper. The still air beneath
the paper is at a higher pressure and a
net upwards force lifts the paper.
As air is blown vigorously between two
sheets of paper held vertically, air flows
at high speed and this creates a region of
low pressure between the two sheets of
papers. The outside air the paper which
is at a higher pressure presses the two
sheets of papers together.
Evidence of Bernoulli’s Principle in our daily lives

5. Demo: Blow It Off
Bend cardboard into a U-shape. Place on table, legs
down, and try to blow it off.
Side view
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Front
view
Fast moving air in the
channel between the card
and the table creates a low
pressure region, pressing the
card downward.

6. Demo: Keep It Up
Objects in a moving steam of fluid are pulled to the
center of the stream because pressure is lower
inside the stream than outside.
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7. Observation Explanation
As air is blown out from the pipe, air
flows at high speed and this creates a
region of low pressure across the top of
the pipe. The still air around the ball is
at a higher pressure and pushes on the
ball and causes it to stay in the air.
As air is blown vigorously between two
ping pong balls, air flows at high speed
and this creates a region of low
pressure between the two balls. The
outside air the balls which is at a higher
pressure presses the two balls together.

8. Demo: Blow the Funnel
Blow hard through a
funnel with a ping pong
ball in the funnel’s
bowl.
Instead of being blown
away, the ball is held
tightly in the bowl.
Ping
Pong
Ball
BLOW
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9. Observation Explanation
As air is blown into the funnel, air flows
at high speed at the narrow passage
and this creates a region of low
pressure at X. The still air beneath the
paper is at a higher pressure and a net
upwards force lifts the ball.
X

10. Observation Explanation
Water flows from a region of high
pressure to a region of low
pressure.
As fluid flows pressure decreases.

11. Observation Explanation
Velocity of fluid at a narrow passage is
faster than at a broad passage.
As the velocity increases, the pressure
decreases (Bernoulli’s Principle)

12. Observation Explanation
Liquid flow As the tube narrows, the fluid flows
more quickly and correspondingly,
pressure in the narrow section
decrease, therefore the water level is
low.

13. Observation Explanation
Air flow As the tube narrows, the fluid flows
more quickly and correspondingly,
pressure in the narrow section
decrease, therefore the water level is
low.

14. Observation Explanation
Air flow
Observe the liquid level and the
pressure difference in the 3 tubes.
Venturi Tube
As air is blown through a tube as shown
in the figure on the left, the region in the
narrow section has a lower pressure. The
external atmospheric pressure pushes
the water to its highest level in this
section.
Water level at C is lower than at A
because as air flows, pressure decreases.

15. Airplane Wing
Pressure difference created by Bernoulli effect creates
upward lift.
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Wing
LIFT FORCE

16. A spinning ball curves
Velocity of air and velocity of ball = opposite
= reduced velocity of air flow = high pressure
Velocity of air and velocity of ball = same
= increased velocity of air flow = low pressure

18. Observation Explanation
Insecticide sprayer /
Perfume sprayer
When the plunger is pushed in, the air
flows at a high velocity through a nozzle.
The flow of air at high velocity creates a
region of low pressure just above the
metal tube. The higher pressure acts on
the surface of the liquid insecticide
causing it to rise up the metal tube. The
insecticide leaves the top of the metal
tube through the nozzle as a fine spray.
Application of Bernoulli’s Principle in our daily lives

19. Observation Explanation
Bunsen burner
When the burner is connected to a gas
supply, the gas flows at high velocity
through a narrow passage in the narrow
nozzle, creating a region of low
pressure. The outside air, which is at
atmospheric pressure is drawn in and
mixes with the gas. The mixture of gas
and air enables the gas to burn
completely to produce a clean, hot, and
smokeless flame.

20. Observation Explanation
Water pump
A jet of water flows at high speed at the
nozzle. This creates low pressure at the
region. Air from the vessel is of high
pressure and therefore is drawn out
from the vessel and into the water
pump.

21. Observation Explanation
Carburetor The air flows past a choke valve, which
controls the quantity of air, into a
narrow a section of the carburetor
where the air velocity increases.
Aerodynamic shape of a car :
i.Creates an upward force that lifts the
car up.
ii.Reduces air friction (less drag)
Theses enable the car to move forward
faster.

22. Observation Explanation
As the wing of a car or a bird moves
forward, the air flows at higher speed
on top of the wing and this creates a
region of low pressure on top of the
wing. The slower air flow beneath the
wing has a higher pressure. The
difference in pressure produces a net
force that pushes the wing up.
The shape of the wing is called
Aerodynamic.

24. Phenomena of Bernoulli’s Principle

25. Blow the Roof
If wind blows hard enough
the low pressure above
can create a large
enough force to lift the
roof off.
New Orlean’s Superdome after hurricane Katrina
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