3.6 berboulli's principle

8/8/2019 3.6 Berboulli's Principle

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3.6 understanding3.6 understanding

Bernoullis PrincipleBernoullis PrincipleLearning Outcome:

State Bernoullis Principle. Explain that a resultant

force exists due to a

difference in fluid pressure.

Describe the application of

Bernoullis Principle.

Solve problems involving

Bernoullis Principle.


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How does an

How does anaeroplane fly ?aeroplane fly ?

Why the aeroplane has to moveWhy the aeroplane has to movefast on a runway before it canfast on a runway before it can

take off ?take off ?


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To understand the principleTo understand the principle

Carry out handsCarry out hands--on activity 3.7 on pg 65on activity 3.7 on pg 65

(a)(a) Blowing in between two pieces of paperBlowing in between two pieces of paper(b)(b) Blow above a piece of paper.Blow above a piece of paper.

(c)(c) Blow through the space between two pingBlow through the space between two ping

pong ballspong balls


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ObservationObservation

Blown airmove faster

Still airmove slower

Lowerpressure

Higherpressure

When the air move faster, the

surrounding pressure becomes lower.

Conclusion :


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Demonstration handsDemonstration hands--on activity 3.8 on pg 66on activity 3.8 on pg 66

Observed the water level in each vertical tubeObserved the water level in each vertical tubewhenwhen

Water is not flowing Water is flowingWater is not flowing Water is flowing


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Please note

Fluid flow faster

through a narrowregion


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ObservationObservation ExplanationExplanation

PX= PY= PZ

PX> PY> PZ

Water flows from aregion of high

pressure to a regionof low pressure

Pressure is thesame when water isnot flowing


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ObservationObservation ExplanationExplanation

PX> PZ > PY

Water flowsmost quickly

through Y ,thus pressureat Y is thelowest.

Pressure is thesame when water isnot flowing

PX= PY= PZ


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Bernoullis PrincipleBernoullis Principle

When the speed of a fluidWhen the speed of a fluid

increasesincreases, the pressure of, the pressure ofthe fluidthe fluid decreasesdecreases andandvice versa.vice versa.

Please note : This Principle isapplicable to flowing fluid only


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Application of Bernoullis PrincipleApplication of Bernoullis Principle

1. The dynamic lift of an aeroplane.1. The dynamic lift of an aeroplane.

Air flowing over an aerofoil-shaped wing will result

in a lifting force on the wing.


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The body isstreamline

The wing isaerofoil

Reduce resistance tothe flow of air

Give the best ratioof lift to drag


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2. Bunsen Burner2. Bunsen Burner

1.Air flows out from the jet X with high velocity.Hence by Bernoullis Principle, its pressure is low.

2. Air of higher pressure from the surrounding rushes

in rapidly into the Bunsen Burner.


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3. Carburetor3. Carburetor

1. Air flows through the narrow passage at the top of thejet with high velocity. Hence by Bernoullis Principle, itspressure is low.

2. The higher atmospheric pressure forces the petrol into the

constriction, mix with air and is sent for burning.

Adevice for mixingair with a fine sprayof liquid fuel


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Can you explain these incidents ?Can you explain these incidents ?

Compare the speed of air in each region

Compare the pressure in each region

Give a conclusion about the resultant force


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EvaluationEvaluation

1. Diagram shows a stream of air flowsthrough a Bernoulli tube.

The correct order of the height of water in thethree tubes is

A T1> T2> T3 C T3 > T1 > T2B T2 > T1 > T3 D T2 > T3 > T1

High pressure Low pressure

Highestpressure

Highestwaterlevel


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2. Diagram shows astream of air flowingthrough a tube .

Which of the following graphsshows the relationshipbetween the water pressure

and the distance, l ?

High pressureLow pressure

Lowestpressure


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3. Diagram shows an upward lift acting on theaerofoil when it moves through layers of airflow.

A by inverting the aerofoilB by moving through a denser air flowC by increasing the velocity of the aerofoil

D by increasing the surface area of the aerofoil

The upward liftcan be increasedby all of thefollowing except


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4. When the whistle is blown, the light sphere will movefrom R to Q.

The movement of the light sphere R is due to

A Air pushes the light sphere upwards.B Velocity of air at R is lower than at Q.C Pressure at R is lower than at Q.

D Density of air at R is greater than at Q

Q

R

blow

Lightsphere


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Home workHome work

Mastery Practice 3.6 pg 102Mastery Practice 3.6 pg 102

Check Your Progress 3.6Check Your Progress 3.6

(Exploring pg 195)(Exploring pg 195)

3.6 berboulli's principle

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