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.
Last updated
Read the Fluid Dynamics notesFree MDCAT chapter notes with key terms363 questions · page 8 of 19
- A. Increase
- B. Decrease
- C. Remain the same
- D. Doubles
Explanation: Correct. Generally, viscosity increases with an increase in temperatureIn summary, the correct option is **a.
Correct answer: Increase- A. 4.9m/s
- B. 9.8 m/s
- C. 4.42 m/s
- D. 3.75 m/s
Explanation: To find the speed of efflux from a hole in a container filled with water, Torricelli's theorem is used: v = \sqrt{2gh}, where g is the…
Correct answer: 4.9m/s- A. 140/60
- B. 120/80
- C. 80/120
- D. 90/60
Explanation: Blood pressure is measured in millimeters of mercury (mmHg) and is expressed as a ratio of systolic pressure (the pressure when the heart…
Correct answer: 120/80- A. Middle
- B. Top right corner
- C. Top left corner
- D. Same flow throughout
Explanation: In a river flow, the water velocity is maximum at the middle due to less friction with the riverbed and banks.
Correct answer: Middle- A. Object is denser than water
- B. Water is denser than object
- C. Either a or b
- D. None of these
Explanation: An object sinks in water if its density is greater than the density of water.
Correct answer: Object is denser than water- A. 2:3
- B. 4:6
- C. 4:9
- D. 2:6
Explanation: The terminal velocity of a spherical object falling through a viscous fluid is directly proportional to the square of its radius.
Correct answer: 4:9- A. 4.9ms-1
- B. 9.8ms-1
- C. 4.42ms-1
- D. 3.75ms-1
Explanation: At the tank mid-height h = 1.00 m, Torricelli's theorem gives v = √(2gh). Using g ≈ 9.8 m/s², v = √(2×9.8×1) = √19.6 ≈ 4.43 m/s.
Correct answer: 4.42ms-1- A. 2.8m/s
- B. 3.7m/s
- C. 6.6m/s
- D. 8.8m/s
Explanation: Continuity requires A1v1= A2v2 , so v2= (A1 /A2 ) = v1 (d12/d2²). With d1 =6, d2=8: v₂= 5×(6²/8²)=5×(36/64)=5×0.5625=2.8125 m/s ≈ 2.8 m/s.
Correct answer: 2.8m/s- A. kgm2 s-1
- B. kgm2 s-2
- C. kgm-1 s-1
- D. kgms-2
Explanation: From F = k r v, rearrange k = F/(r v). F has units N = kg·m·s⁻², r is m and v is m·s⁻¹, so k units = (kg·m·s⁻²)/(m·m·s⁻¹) = kg·m⁻¹·s⁻¹.
Correct answer: kgm-1 s-1- A. 8cm/s
- B. 16cm/s
- C. 24cm/s
- D. 32cm/s
Explanation: Volume scales ∝ r³, combining 8 equal drops doubles the radius (since 8×r³ → (2r)³).
Correct answer: 32cm/s- A. 2.5m/s
- B. 24m/s
- C. 4.44m/s
- D. Cannot be calculated unless the area of the hole is given
Explanation: Torricelli's theorem: v = √(2 g h). With g ≈ 10 m/s² and h = 30 m, v = √(2×10×30) = √600 ≈ 24.49 m/s. Area is irrelevant for efflux speed.
Correct answer: 24m/s- A. 4.95×10⁻³ m³/s
- B. 4.9 m3/s
- C. 7.0 m³/s
- D. 49 m³/s
Explanation: Volumetric flow Q = A v = π r² v. With r = 0.015 m: A = π(0.015) ² ≈ 7.07×10⁻⁴ m². Q = 7.07×10⁻⁴×7 ≈ 4.95×10⁻³ m³/s ≈ 4.9×10⁻³ m³/s.
Correct answer: 4.95×10⁻³ m³/s- A. A₁/A₂
- B. A₂/A₁
- C. √A₁/A₂
- D. √A₂/A₁
Explanation: Continuity for incompressible flow gives A₁V₁ = A₂V₂ ⇒ V₂/V₁= A₁ /A₂ . Thus the speeds are inversely proportional to thecross-sectional…
Correct answer: A₂/A₁- A. 2/3
- B. 4/3
- C. 3/2
- D. 3
Explanation: Take equal masses m of densities 1 and 2. Total mass = 2m; total volume = m/1 + m/2 = 1.5 m ⇒ density = (2m)/(1.5 m) = 4/3.
Correct answer: 4/3- A. Acceleration due to gravity
- B. Height of the liquid column
- C. Area of the bottom surface
- D. Nature of the liquid
Explanation: Hydrostatic pressure p = ρ g h is independent of the area of the container's base. It depends on fluid density, gravity and depth.
Correct answer: Area of the bottom surface- A. 20%
- B. 35%
- C. 10%
- D. 25%
Explanation: Fraction submerged =ρᵢcₑ / ρwₐₜₑᵣ = 900/1000 = 0.9 ⇒ 90% submerged. So 10% of the volume is above water: (100% − 90%) = 10%.
Correct answer: 10%- A. High thickness & high density in small pipe
- B. High thickness & low density in small pipe
- C. Low thickness & low density in large pipe
- D. Low thickness & high density in large pipe
Explanation: Laminar flow occurs at low Reynolds number, Re= ρvD/μ. High viscosity (large μ) and small pipe diameter D reduce Re; lower fluid density ρ…
Correct answer: High thickness & low density in small pipe- A. 4 times faster
- B. 1/4 times slower
- C. 2 times faster
- D. Half as fast
Explanation: If the diameter is halved, the cross-sectional area scales with diameter², so the area reduces by a factor of 4; continuity requires the…
Correct answer: 4 times faster- A. Horizontal pipe
- B. Vertical with A on top
- C. Vertical with B on top
- D. All cases
Explanation: If cross-sectional area and flow conditions remain identical, the local flow speed can be the same regardless of orientation.
Correct answer: All cases- A. 3.0 m/s
- B. 3.82 m/s
- C. 5.7 m/s
- D. 2.86 m/s
Explanation: V2= v1 (A1 /A2). Convert areas: A1=4.20 cm², A2=7.60 cm² ⇒ v2 = 5.18×(4.20/7.60) = 5.18×0.5526 ≈ 2.86 m/s.
Correct answer: 2.86 m/s