Formative Practice 2.6 (Textbook) – Physics Form 5 Chapter 2 (Pressure)

Question 1:
State Bernoulli’s principle.

Answer:
Bernoulli’s principle states that when the velocity of the flow of a fluid increases, the pressure in the fluid decreases.

Question 2:
Explain three ways of using a piece of A4 paper to demonstrate Bernoulli’s principle.

Answer:

Question 3:
Figure 2.53 shows the cross section of the wing of an aeroplane when the aeroplane is accelerating along the runway and when it begins to take off from the runway.


With the aid of labelled diagrams, explain how the lift force is produced when the aeroplane takes off.
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Answer:



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The shape of the aerofoil causes air to flow:
– at high velocity above the upper section of the wing of the aircraft
– at lower velocity below the lower section of the wing of the aircraft

According to Bernoulli’s principle:
– above the upper section of the wing is a region of low air pressure
– below the lower section of the wing is a region of high pressure
– this difference in air pressure produces a resultant force upwards to lift the aircraft into the air

The wing is inclined to produce an angle of attack:
– the flow of air below the wing experiences an action force and is deflected
– the wing experiences a reaction force that contributes to the lift force