S M K Pahi
Bidang sains dan matematik
LESSON 3.6 - Application Bernoulli Principal
LESSON 3.6 - Understanding
Bernoulli’s principle.
Bernoulli’s principle.
Activities to show Bernoulli’s Principle
Bernoulli’s principle states that The pressure of a
moving liquid decreases as the speed of the fluid
increases and vice versa.
Activity 1
The conditions which enable the Berrnoulli’s
Principle to use
(1) The fluid is incompressible and flows easily
(2) The fluid is streamline or in layers,i.e. there are
no eddies or turbulence
When the air is blown up in the surface of a piece of
paper,its observed that the paper moves up.
This happened because the air moved at a very high
velocity.
According to Bernoulli’s Principle , the pressure of the
moving air decreases as the speed of the air
increases .
The higher atmospheric pressure which acts at the
bottom of the paper pushes up the paper.
Factors affecting the speed of the moving liquid.
(1) The speed of moving object increases as the
area of moving fluid decreases
(2) The speed of moving object increases as the
distance of moving fluid
Bernoulli’s principle and the law of conservation
of energy
Activity 2
Energy is always conserved and this also applies to
fluids, wether static or in motion. A fluid in motion has
kinetic energy. This kinetic energy imparted to the
fluid comes at the expense of the pressure of the
fluid. Thus, when the speed (kinetic energy) of the
fluid increases, its pressure decreases.
When the air is blown harder through the straw ,
The two ping-pong balls will move closely to each
other.
The air moved at a very high velocity between the
balls.
According to Bernoulli’s Principle , the pressure of
the moving air decreases as the speed of the air
increases .
The higher atmospheric pressure caused the pingpong balls closer to each other.
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S M K Pahi
Bidang sains dan matematik
LESSON 3.6 - Application Bernoulli Principal
Activity 3
When the air blows harder ,the ball is not falling
down.
It is because the air moved at a very high velocity
between the balls and the wall of the filter tunnel.
According to Bernoulli’s Principle , the pressure of the
moving air decreases as the speed of the air
increases .
The bottom of the ball has the higher atmospheric
pressure which can hold the ball from falling down.
Activity 4- Using Venturi tubes
Use of Bernoulli’s Principle in Everyday Life
Mark the water level in the vertical tubes P,Q and R in
the following figures.
(1) A person who stands near a railway feels like
falling into it when suddenly a train moves with
a high speed passes him. It is because the
velocity of the air in front of him increases.
According to Bernoulli’s Principle , the pressure
of the moving air decreases as the speed of the
air increases. The higher atmospheric pressure
behind pushes him forward.
(2) When two speed bots move faster and closely
to each other, an accident may be occurred. It is
because the water moved at a very high
velocity between the boats. According to
Bernoulli’s Principle , the pressure of the moving
air decreases as the speed of the air increases .
The higher water pressure on either sides of the
boats caused its closer to each other .
(3) A table-tennis player often gives the ball ‘top
spin’ enabling a hard drive to be hit over the net
and land on the table. A ball hit with spin
swerves considerably in its path.
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Bidang sains dan matematik
LESSON 3.6 - Application Bernoulli Principal
(2) Insect Piston Spray
The figure above shows the rotating surface of
the ball, due to spin, and v the air velocity. The
spin of the ball carry some air with it, and the
resultant velocity of air on the upper surface will
therefore be less than v, and the lower surface
greater than v. There is therefore a pressure
difference between the upper and lower
surfaces which deflects the ball, originally hit
from right to left in downwards direction
When the piston is pushed, air is forced out through
the jet of gas at a high speed.
According to Bernoulli’s Principle , the pressure of the
moving air decreases as the speed of the air
increases .
The higher atmospheric pressure in the insect poison
container will push the insect poison liquid up
through the narrow metallic tube.
Use of Bernoulli’s Principle in
(1)
(3) Filter pump
Bunsen burner
When the jet of gas flows out from the nozzle with
high velocity , the pressure in the Bunsen burner
becomes low(Bernoulli’s principle)
A higher external atmospheric pressure will be
sucked into the air hole and be mixed with the gas .
The mixture of gas and air allows more complete
combustion of the gas.
Water from a tap flows at high speed out of the jet of
water(nozzle).
According to Bernoulli’s Principle , the pressure of the
moving air decreases as the speed of the air
increases
The higher air ssure in the vessel ‘pumps’ air from the
side tube to which the vessel is connected.
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S M K Pahi
Bidang sains dan matematik
LESSON 3.6 - Application Bernoulli Principal
(4) Carburettor
TUTORIAL 6
1
The figure shows two polystyrene spheres are
hung by a string respectively.
When the air is blown harder through the
straw , the balls will
A
B
C
When the engine is switched on , air is sucked into
the the venture tube.
Fast moving air in the narrow section of the tube
causes a low pressure at this region.
The higher atmospheric pressure in the petrol
compartment will push the petrol into the region.
The petrol will mix with air before it flows into the
cylinder engine for combustion.
remain stationary
move closely to each other
move far apart to each other
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The figure shows the flow a liquid through a
Bernoulli tube. The smallest pressure of the
liquid is at point……
3
The figure shows water flows through a Venturi
tubes from point P to point Q.
In which vertical tubes A ,B,C or D the pressure
of water is very low?
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The figure shows an arrangement of apparatus
which is used to show the Bernoulli’s Principle.
(5) Aerofoil
The above figure shows the streamlines round a thin
wing at an angle of attack to the air stream.
It will be seen that the path of air is longer over the
upper surface than the lower, and therefore the speed
is greater on the upper surface. The lift is produced
by the difference in pressure between the two
surfaces , which helps the plane to take-off.
In addition to its use in airplanes, aerofoil is also used
in racing cars. In this case, the downward force helps
to stabilize the car at high speeds.
When the air is blown, the level of water in tube
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Bidang sains dan matematik
LESSON 3.6 - Application Bernoulli Principal
A
B
C
D
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X will the highest
Y will the highest
Z will the highest
X,Y and Z will the same
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Which of the following is based on Bernoulli’s
Principle?
A
B
C
The figure shows water rising up the tubes X,Y
and Z if the air is blown.
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Syringe
Drinking straw
Bunsen burner
The figure shows a water spray that is produced
when the air flows through the jet.
Which of the following is true regarding the
water level in tube X,Y and Z?
A
B
C
D
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Water level in X < Water level in Y < Water
level in Z
Water level in X < Water level in Z < Water
level in Y
Water level in Z < Water level in Y < Water
level in X
Water level in Y < Water level in Z < Water
level in X
Which of the following is true?
A
B
C
The figure shows the wing of an aeroplane
which is moving with a uniform acceleration in
the direction shown by the arrow.
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B
C
D
The figure shows a motion a ball when it is
kicked by a player.
The motion of the ball can be explained by
Which of the following is true?
A
According to Pascal’s Principle ,the that
above system produces a water spray.
The air pressure at Q is higher than that at
P
The velocity of air at Q is higher than that
at P
A
B
C
D
The uplift force is higher than the weight of
object
The resultant force in direction of the
motion of the object is zero
The pressure in region P is higher than in
region Q
The velocity of air in region P is higher
than in region Q.
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5
Principle of conservation of momentum
Principle of conservation of energy
Archimedes’ principle
Bernoulli’s principle
A ball which is thrown forward in a spin moves
in a curve , as shown in the figure.
S M K Pahi
Bidang sains dan matematik
LESSON 3.6 - Application Bernoulli Principal
tube X until water reaches level C.
The curved path taken by the ball is due to
A
B
C
D
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equilibrium of forces
Bernoulli’s principle
Archimedes’ principle
principle of conservation of momentum
Figure(a)
The figure shows a ping-pong ball that does not
fall when the water flows.
(a) (i)
Mark on the Figure(a) ,the possible
water levels for tube Y and Z.
(ii) Calculate the pressure at P exerted
by the column of water if D is 10 cm
height from P.
[ Density of water = 1000 kg m-3]
Which principle explains the figure?
A
B
C
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(iii) If the cross –sectional area of tube X
is 2 x 10-5 m2 , calculate the force
acted by by the column of water in
tube X.
Which of the following instruments is not based
on Bernoulli’s principle?
A
B
C
D
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Pascal’s principle
Bernoulli’s principle
Archimedes’ principle
Filter pump
Car carburetor
Rubber plunger
Wing of aeroplane
Figure(b) shows the rubber stoppers at both
ends of tube AB are taken away so that the
water can flow uniformly from end A to end B,
then water water tube X rises until level D.
Figure(a) shows a horizontal tube AB both ends
closed with rubber stoppers is fixed with three
vertical tubes X,Y and Z. Water is poured into
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S M K Pahi
Bidang sains dan matematik
LESSON 3.6 - Application Bernoulli Principal
13
Figure(a) shows a cross section of the wing of
an aeroplane . The slat and the flat can be
moved during flying.
Figure(a)
Figure (b)
Mark on the Figure(b) ,the possible
water levels for yube Y and tube Z.
(ii) Give one reason for your answer in
b(i)
(a) Name the shape of the the wing.
(b) (i)
………………………………………………
…………………………………………
…………………………………………
Figure(c) shows the apparatus is modified so
that the middle part of the horizontal tube
becomes narrow. Water slows uniformly from
from end end G to end H of the tube and it is
found that the water level of tube X is at E.
Figure(b)
(b) Figure(b) shows the cross section of the
wing with its flap extended after take-off.
(i) Mark the region of high velocity with
the letter S .
(ii) Based on the Figure(b) , explain how
the uplift force is produced to help the
plane take-off.
………………………………………..
………………………………………..
Figure (c)
(c)
(i)
(ii)
………………………………………..
Mark on the Figure(c) , the possible
water levels of tube Y and tube Z.
Compare the velocity of water at Q
and R.
………………………………………..
………………………………………..
………………………………………...
(iii) What is the relationship between
velocity and pressure of water along
the horizontal tube GH.
………………………………………..
………………………………………..
………………………………………..
(iii) Name the principle involved in(b)(ii)
…………………………………………
………………………………………….
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S M K Pahi
Bidang sains dan matematik
LESSON 3.6 - Application Bernoulli Principal
(iv) Explain why the surface area of the
wing is increased by extends slat
and flat after the airplane has taken
off.
Figure(a)
………………………………………..
………………………………………..
………………………………………..
………………………………………..
Figure(b)
………………………………………..
(a) Observe the figures and state the
similarities between the positions of the
the ping-pong ball and the boats.
………………………………………..
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………………………………………..
………………………………………………
………………………………………..
……………………………………………….
(b) (i) State three physical quantities
involved to cause the change of the
positions of the ping-pong ball and
the boats.
Figure(a) shows the positions of a ping-pong
ball before and after a stream of water from a
tap is flown.
Figure(b) shows the positions of two toy boats
before and after a stream of water from a hose
is directed between the boats.
………………………………………
(ii)
………………………………………
State the relationship between the
physical quantities that is stated in
b(i)
………………………………………..
………………………………………
(iii) Name the principle involved in b(ii)
(c)
………………………………………
If the ping-pong ball is replaced by the
metal ball,
(i) what will happen to position of the
ping –pong ball when the tap is
opened.
(ii)
……………………………………….
Give a reason for your answer in
(c)(i).
………………………………………
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S M K Pahi
Bidang sains dan matematik
LESSON 3.6 - Application Bernoulli Principal
15
……………………………..
Figure(a) shows a piece of paper hanging from
a retort stand. When air flows from the nozzle of
an air pump, the paper changes its position as
shown in Figure(b).
……………………………..
……………………………..
(e) Name the principle that causes
the the observations in Figure(b)
…………………………………..
(f) Name one piece of apparatus in
a school laboratory which uses
the principle in(e).
Figure(a)
…………………………………..
Figure(b)
(a) Compare the position of paper in Figure(a)
And Figure(b)
……………………………………………....
………………………………………………
………………………………………………
(b) F is a force that causes the paper to
change its position.
In box, X, on Figure(b) , indicate and label
the direction of F that acts on the paper.
(c)
Explain how F is produced?
………………………………………..
………………………………………..
………………………………………..
(d) (i) Compared to the position
of the paper in Figure(b), how does
the position of the paper change
when the air flows faster?
……………………………..
(ii)
……………………………..
Give a reason for your
answer in d(i).
……………………………..
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