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Fluid dynamics
5 Class 11 Physics questions with answers and explanations.
Printable worksheet with answer key
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The equation of continuity for an incompressible fluid says:
- 1 A v is constant
- 2 P v is constant
- 3 A + v is constant
- 4 A / v is constant
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Correct answer: A v is constant
The flow rate A v is the same at all points of a pipe.
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Water flows through a pipe of area 4 cm2 at 2 m/s into a section of area 2 cm2. What is the new speed?
- 1 8 m/s
- 2 1 m/s
- 3 4 m/s
- 4 2 m/s
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Bernoulli's principle says that where the speed of a fluid is higher, the pressure is:
- 1 Lower
- 2 Infinite
- 3 Higher
- 4 The same
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Correct answer: Lower
Along a line of flow, faster flow means lower pressure.
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Viscosity of a liquid generally:
- 1 Decreases with temperature
- 2 Increases with temperature
- 3 Is not affected
- 4 Becomes zero when heated
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Correct answer: Decreases with temperature
Liquids become less viscous as they get hotter.
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An aeroplane wing gets lift because air above it moves:
- 1 Backwards
- 2 At the same speed
- 3 Slower, with higher pressure
- 4 Faster, with lower pressure
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Correct answer: Faster, with lower pressure
Faster air above gives lower pressure, so there is a net upward force.