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Fluid Statics and Dynamics MCQs — Physics (page 3)

180 multiple-choice questions on Fluid Statics and Dynamics from Physics, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

51. Flow is likely to become turbulent when:

  1. the fluid is ideal
  2. the pipe is very wide and flow slow
  3. the speed is very low
  4. the speed is high

Answer: D) the speed is high

Explanation: Above a critical speed. SLO P-11-B-35 · Knowledge

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52. For an incompressible fluid, rho1A1v1 = rho2A2v2 reduces to A1v1 = A2v2 because:

  1. v1 = v2
  2. mass is not conserved
  3. A1 = A2
  4. rho1 = rho2

Answer: D) rho1 = rho2

Explanation: Constant density cancels. SLO P-11-B-38 · Application

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53. A sphere falling through oil reaches terminal velocity when:

  1. weight = 0
  2. weight = upthrust + viscous drag
  3. drag = 0
  4. upthrust = 0

Answer: B) weight = upthrust + viscous drag

Explanation: Net force zero, so no acceleration. SLO P-11-B-42 · Understanding

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54. An aircraft wing produces lift because:

  1. air is heavier below
  2. air flows faster over the curved top, lowering the pressure above
  3. the engines push it up
  4. the wing is light

Answer: B) air flows faster over the curved top, lowering the pressure above

Explanation: Pressure below exceeds pressure above. SLO P-11-B-44 · Application

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55. Water flows at 1.2 m/s through a pipe of cross-section 0.05 m^2. The volume flow rate is:

  1. 0.006 m^3/s
  2. 0.12 m^3/s
  3. 0.06 m^3/s
  4. 0.6 m^3/s

Answer: C) 0.06 m^3/s

Explanation: Flow rate = Av = 0.06 m^3/s. SLO P-11-B-36 · Application

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56. A fluid of density 1.2 kg/m^3 flows at 10 m/s through a pipe of area 0.5 m^2. The mass flow rate is:

  1. 0.6 kg/s
  2. 12 kg/s
  3. 6 kg/s
  4. 60 kg/s

Answer: C) 6 kg/s

Explanation: Mass flow rate = rho A v = 6 kg/s. SLO P-11-B-38 · Application

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57. The viscosity of a superfluid is:

  1. negative
  2. the same as water
  3. zero
  4. very large

Answer: C) zero

Explanation: Definition. SLO P-11-B-43 · Understanding

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58. A nozzle fitted on a fire hose is used to:

  1. filter the water
  2. reduce the speed of water
  3. increase the exit speed of water
  4. heat the water

Answer: C) increase the exit speed of water

Explanation: The nozzle has a small exit area. SLO P-11-B-37 · Understanding

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59. An umbrella turning inside out in strong wind is due to:

  1. the umbrella being magnetic
  2. higher pressure above it
  3. lower pressure above it from the faster air flow
  4. rain weight

Answer: C) lower pressure above it from the faster air flow

Explanation: Pressure below exceeds pressure above. SLO P-11-B-39 · Application

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60. Without viscosity, a stirred cup of tea would:

  1. keep swirling for ever
  2. freeze
  3. boil
  4. stop immediately

Answer: A) keep swirling for ever

Explanation: Viscosity dissipates the swirling motion. SLO P-11-B-41 · Understanding

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61. A solid sinks in water if:

  1. its volume is large
  2. it is hollow
  3. its density is less than that of water
  4. its density is greater than that of water

Answer: D) its density is greater than that of water

Explanation: Its weight exceeds the maximum upthrust. SLO P-11-B-33 · Application

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62. When a hose is squeezed, the volume of water leaving per second (with the tap unchanged):

  1. stays about the same
  2. becomes zero
  3. halves
  4. doubles

Answer: A) stays about the same

Explanation: Only the speed changes (ideal case). SLO P-11-B-37 · Understanding

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63. The pressure difference that pushes a fluid from a wide to a narrow pipe is what:

  1. accelerates the fluid
  2. heats the fluid
  3. compresses the fluid
  4. slows the fluid

Answer: A) accelerates the fluid

Explanation: Net force = pressure difference × area. SLO P-11-B-39 · Application

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64. A superfluid can 'creep' over the walls of its container because:

  1. it evaporates rapidly
  2. gravity reverses
  3. it is magnetic
  4. with no viscosity, a thin film climbs the walls and flows out

Answer: D) with no viscosity, a thin film climbs the walls and flows out

Explanation: The container can empty itself. SLO P-11-B-43 · Understanding

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65. A body of volume 1 10^-4 m^3 is fully immersed in a liquid of density 13,600 kg/m^3. The upthrust on it is (g = 9.8):

  1. 26.7 N
  2. 133 N
  3. 1.33 N
  4. 13.3 N

Answer: D) 13.3 N

Explanation: Upthrust = weight of liquid displaced = rho V g = 13.3 N. SLO P-11-B-33 · Application

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66. Water flows at 1.5 m/s through a pipe section of area 6 m^2 into a section of area 9 m^2. Its speed there is:

  1. 0.5 m/s
  2. 2 m/s
  3. 1 m/s
  4. 2.25 m/s

Answer: C) 1 m/s

Explanation: A1v1 = A2v2 Rightarrow v2 = 6 1.59 = 1 m/s. SLO P-11-B-36 · Application

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67. Viscosity is:

  1. the internal friction of a fluid that resists flow
  2. the pressure of a fluid
  3. the buoyancy of a fluid
  4. the density of a fluid

Answer: A) the internal friction of a fluid that resists flow

Explanation: It opposes relative motion of layers. SLO P-11-B-41 · Understanding

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68. Streamlines that are close together indicate:

  1. high flow speed
  2. zero speed
  3. high viscosity
  4. low flow speed

Answer: A) high flow speed

Explanation: Same flow squeezed through a smaller area. SLO P-11-B-35 · Knowledge

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69. In a car engine carburettor, fuel is drawn in because:

  1. gravity pulls it up
  2. heat expands it
  3. air speeding through a narrow throat lowers the pressure
  4. fuel is pumped by a piston

Answer: C) air speeding through a narrow throat lowers the pressure

Explanation: A Venturi duct. SLO P-11-B-44 · Application

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70. For a fluid at rest, Bernoulli's equation reduces to:

  1. A1v1 = A2v2
  2. P2 - P1 = rho g(h1 - h2)
  3. v = 2gh
  4. P = 0

Answer: B) P2 - P1 = rho g(h1 - h2)

Explanation: The hydrostatic pressure formula. SLO P-11-B-40 · Application

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71. The Plimsoll mark 'TF' (tropical fresh) is the highest line because:

  1. it is decoration
  2. warm fresh water is the least dense
  3. the ship is lightest in the tropics
  4. fresh water is the densest

Answer: B) warm fresh water is the least dense

Explanation: The ship floats lowest there. SLO P-11-B-34 · Application

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72. Upthrust arises because:

  1. pressure in a fluid increases with depth, so the push upward on the bottom is greater
  2. fluids pull objects up
  3. fluids have no weight
  4. gravity is weaker in fluids

Answer: A) pressure in a fluid increases with depth, so the push upward on the bottom is greater

Explanation: Delta p = rho g h. SLO P-11-B-33 · Application

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73. The 'fountain effect' of superfluid helium is:

  1. helium freezing into ice
  2. helium becoming a gas instantly
  3. a jet of helium shooting up when it is gently heated in a porous tube
  4. helium becoming viscous

Answer: C) a jet of helium shooting up when it is gently heated in a porous tube

Explanation: A striking superfluid demonstration. SLO P-11-B-43 · Understanding

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74. Ordinary liquids stop swirling after stirring because of:

  1. surface tension only
  2. upthrust
  3. superfluidity
  4. viscosity

Answer: D) viscosity

Explanation: A superfluid lacks this. SLO P-11-B-43 · Understanding

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75. The physics principle behind squeezing a hose is:

  1. Hooke's law
  2. the equation of continuity
  3. Archimedes' principle
  4. Pascal's law only

Answer: B) the equation of continuity

Explanation: A1v1 = A2v2. SLO P-11-B-37 · Understanding

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