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Free Fluid Dynamics MCQs with Answers

363 Fluid Dynamics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Fluid flow is described through speed, pressure and density, including steady flow and the equation of continuity for conserving mass. Bernoulli's equation relates pressure, speed and height, while fluid drag and terminal velocity explain why a falling object eventually moves at constant speed when drag balances its weight.

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Terminal VelocityFluid DragFluid FlowEquation of ContinuityBernoulli's Equation
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363 questions · page 4 of 19

61. According to Pascal's law the pressure of gas in a vessel is

  • A. Different in different direction
  • B. Same in all direction
  • C. Same only along opposite directions
  • D. Same only along normal directions

Explanation: Pascal's law states that in a confined fluid, pressure is transmitted equally in all directions.

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Correct answer: Same only along normal directions

62. Bernoulli's equation is the fundamental equation in fluid dynamics that relates pressure of fluid to its speed and height.According to the Bernoulli's equation, where the speed of the fluid is high, the pressure will be

  • A. Low.
  • B. Zero.
  • C. High.
  • D. Constant.

Explanation: According to Bernoulli's equation, in a streamline flow, the sum of the pressure energy, kinetic energy, and potential energy per unit…

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Correct answer: Low.

63. Bernoullie's equation is the fundamental equation in fluid dynamics that relates pressure of fluid to its speed and height .According to Bernoulli's equation, when the speed of the fluid is high, then the pressure will be

  • A. Low
  • B. Zero
  • C. High
  • D. Constant

Explanation: According to Bernoulli's equation, when the speed of a fluid increases, the pressure within the fluid decreases.

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Correct answer: Low

64. All of the following are applications of Bernoulli's effect EXCEPT

  • A. Aerofoil.
  • B. Atomizer.
  • C. Venturi meter.
  • D. Vacuum cleaner.

Explanation: The correct answer is vacuum cleaner. Bernoulli's principle explains how an increase in the speed of a fluid occurs simultaneously with a…

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Correct answer: Vacuum cleaner.

65. The CORRECT statement in the light of Bernoulli's theorem is that the

  • A. Speed of the fluid is low at low pressure.
  • B. Speed of the fluid is high at low pressure.
  • C. Pressure of a fluid is independent of its speed.
  • D. Theorem is valid only for turbulent flow of a liquid.

Explanation: According to Bernoulli's theorem, in a steady, ideal flow of an incompressible fluid with no viscosity, the sum of the pressure energy…

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Correct answer: Speed of the fluid is high at low pressure.

66. When an aeroplane is flying, the air moves from the top and the bottom of the wings. The air moving over the top of the wings is faster due to which the pressure above the wings will

  • A. Be low.
  • B. Be high.
  • C. Be zero.
  • D. Vary unpredictably.

Explanation: The correct answer is that the pressure above the wings will be low. This is due to Bernoulli's principle, which states that as the speed…

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Correct answer: Be low.

67. According to the Bernoulli's principle, when the pressure decreases during the flow of fluid through different sections of a pipe, then the speed of the fluid will

  • A. Increase
  • B. Decrease
  • C. Become zero
  • D. Remain the same

Explanation: According to Bernoulli's principle, when a fluid flows through a pipe and experiences a decrease in pressure, the speed of the fluid…

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Correct answer: Increase

68. Which of the following effects is observed in a Venturi metre, when liquid flows through thenarrow section of the pipe?

  • A. Pressure is reduced
  • B. Pressure is increased
  • C. Viscosity is increased
  • D. Viscosity is decreased

Explanation: The correct answer is that pressure is reduced. In a Venturi meter, when a liquid flows through the narrow section, its velocity…

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Correct answer: Pressure is reduced

69. In a cement factory, a viscous liquid flows through a pipe with an area of cross-section 6 m2 at a velocity of 8 m/s.When this fluid moves forward, the area of cross-section of the pipe decreases to 4 m2 The velocity of the liquid will now be

  • A. 3 m/s.
  • B. 12 m/s.
  • C. 18 m/s.
  • D. 24 m/s.

Explanation: The principle of continuity for incompressible fluid flow states that the product of the cross-sectional area and velocity must remain…

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Correct answer: 12 m/s.

70. The equation of continuity of a fluid is related to the conservation of

  • A. Mass
  • B. Energy
  • C. Momentum
  • D. Angular momentum.

Explanation: The equation of continuity expresses the conservation of mass in fluid dynamics.

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Correct answer: Mass

71. In a cement factory, a viscous liquid flows through a pipe with an area of cross-section 6 m² at a velocity of 8 m/s.When this fluid moves forward, the area of cross-section of the pipe decre velocity of the liquid will now be 4 m² The

  • A. 3 m/s.
  • B. 12 m/s.
  • C. 18 m/s.
  • D. 24 m/s.

Explanation: The principle of conservation of mass for a fluid in a closed system is given by the equation: A1 * V1 = A2 * V2, where A1 and V1 are the…

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Correct answer: 12 m/s.

72. According to the equation of continuity, if the cross-sectional area of a pipe decreases, then the speed of the fluid passing through it

  • A. Increases
  • B. Decreases
  • C. Remains the same
  • D. Varies unpredictably

Explanation: The equation of continuity states that the mass flow rate must be constant in a closed system.

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Correct answer: Increases

73. In a fire fighting machine, a jet is attached to the head of water pipes to increase the

  • A. Mass of water flowing out of it.
  • B. Volume of water flowing out of it.
  • C. Velocity of water flowing out of it.
  • D. Distance covered by water flowing out of it.

Explanation: The correct answer is Option C: The jet is designed to increase the velocity of water flowing out of it.

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Correct answer: Velocity of water flowing out of it.

74. An industrial liquid flows through a section of a pipe with an area of cross-section 2 m2 at a velocity of 10 m/s. If at a certain section the area of cross-section decreases to 1 m2, then the velocity of the liquid will be

  • A. 5 m/s
  • B. 10 m/s
  • C. 15 m/s
  • D. 20 m/s

Explanation: According to the principle of continuity for fluid flow, the product of the cross-sectional area and velocity of a fluid must remain…

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Correct answer: 20 m/s

75. In a cement factory, a viscous liquid flows through a pipe with an area of cross-section 6 m2at a velocity of 8 m/s. When this fluid moves forward, the area of cross-section of the pipe decreases to 4 m2 The velocity of the liquid will now be

  • A. 12 m/s.
  • B. 3 m/s.
  • C. 18 m/s.
  • D. 24 m/s.

Explanation: To solve this problem, use the principle of continuity, which states that the product of the cross-sectional area and velocity of a fluid…

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Correct answer: 12 m/s.

76. A rocket is made to travel at a high speed by making the ejection nozzle narrow. This phenomenon is based on

  • A. Turbulent flow.
  • B. Terminal velocity.
  • C. Torricelli's theorem.
  • D. Equation of continuity.

Explanation: The correct answer is the equation of continuity. This principle of fluid dynamics explains that as a fluid flows through a pipe, if the…

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Correct answer: Equation of continuity.

77. The drag force on an object when it is moving in a fluid is 'F'. If the velocity of the object becomes double, then the value of force will become

  • A. F / 4
  • B. F / 2
  • C. F
  • D. 2F

Explanation: In fluid dynamics, the drag force on an object moving through a fluid is typically proportional to the square of the velocity of the…

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Correct answer: 2F

78. Which of the given has the least coefficient of viscosity

  • A. milk
  • B. water
  • C. tar coal
  • D. engine oil

Explanation: The coefficient of viscosity are given as followsMilk: 1.5 to 10 mPa·s ∵Pa.s=pascal-secondWater: 0.001 Pa·s Coal Tar: 10,000 to 50,000…

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Correct answer: water

79. The rain drop falling from the sky reach the ground with

  • A. constant acceleration
  • B. terminal velocity
  • C. constant pressure
  • D. variable acceleration

Explanation: As a raindrop falls, it speeds up due to gravity. But as it falls faster, air resistance slows it down.

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Correct answer: terminal velocity

80. Terminal velocity is

  • A. uniform
  • B. maximum
  • C. uniform and maximum
  • D. neither uniform and maximum

Explanation: Terminal velocity is constant speed achieved by an object falling through a fluid (like air) when the force of gravity pulling it down is…

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Correct answer: uniform and maximum
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