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Fluid dynamics
Class 11 · Physics · 5 questions
Name: ____________________ Date: ____________
The equation of continuity for an incompressible fluid says:
- A A v is constant
- B P v is constant
- C A + v is constant
- D A / v is constant
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?
- A 8 m/s
- B 1 m/s
- C 4 m/s
- D 2 m/s
Bernoulli's principle says that where the speed of a fluid is higher, the pressure is:
- A Lower
- B Infinite
- C Higher
- D The same
Viscosity of a liquid generally:
- A Decreases with temperature
- B Increases with temperature
- C Is not affected
- D Becomes zero when heated
An aeroplane wing gets lift because air above it moves:
- A Backwards
- B At the same speed
- C Slower, with higher pressure
- D Faster, with lower pressure
Answer key
1. A, 2. C, 3. A, 4. A, 5. D
The flow rate A v is the same at all points of a pipe.
A1 v1 = A2 v2, so v2 = 4 x 2 / 2 = 4 m/s.
Along a line of flow, faster flow means lower pressure.
Liquids become less viscous as they get hotter.
Faster air above gives lower pressure, so there is a net upward force.