3.6 bernoulli principle

(3.6) Bernoulli’s (3.6) Bernoulli’s PrinciplePrinciple

Idea

• Why;

Idea

BERNOULLI’S PRINCIPLE

1. Daily situation : a) The roof of a house being lifted by strong winds.

State that;• When the speed of a fluid increases, When the speed of a fluid increases,

the pressure of the fluid decrease the pressure of the fluid decrease and vice versa.and vice versa.

Bernoulli’s PrincipleBernoulli’s Principle

APPLICATIONAPPLICATION

1. Aerofoil shape2.2. Bunsen Burner

3.3. CarburetorsCarburetors4.4. Sports

4. Uses of Bernoulli’s Principle :

a) Aerofoil

- when an aeroplane moves forward,

the velocity of air at upper part of

wing is higher than at the bottom part.

- therefore, lower pressure of air is

produced at upper part of wing and

higher pressure at bottom part of wing.

- difference in pressure produces uplift

force that lifts up the aeroplane.

b) Bunsen burner

The pressure of fast moving gas stream from the nozzle is less than the surrounding atmospheric pressure.

The difference in pressure causes air to be drawn into the burner tube.

c) Car carburator

d) Insecticide sprayer

Exercise;

Exam format question;Exam format question;

a) What is meant by speed?

b) Based on diagram 5.1 and 5.2 ;• i) state two similarities for the situations in diagram 5.1 & 5.2.• ii) compare the air pressure above and below the paper when air is

blown.• iii) Relate the speed of the air to the pressure of the air.

c) Name the principle involved in b (iii)

The diagram 5.1 show the situation of a sheet of paper before and when it is blown. Diagram 5.2 show the situation of the canopy before the lorry moves and when the lorry moves at high speed.

• d) Diagram 5.3 shows an instrument used to measure the speed of air.

• In diagram 5.3, the levels of coloured water in the U-tube are the same before air flows.

(i) Compare the speeds of air at P and Q.

(ii) Mark the water levels in the U-tube in diagram 5.3 while air flows.