FSc Part 1 Physics chapter 6: Fluid dynamics MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

21 exam-style questions on Fluid dynamics, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

21 questions · 2 topics · 10 per test

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What chapter 6 covers

Ten Fluid dynamics questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. Smoke from an incense stick rises smoothly at first, but higher up it breaks into irregular swirls. The swirling upper part is an example of

  1. A
    streamline flow
  2. B
    laminar flow
  3. C
    turbulent flow
  4. D
    ideal fluid flow
Show answer

Answer: C. As the smoke speeds up, the smooth (laminar or streamline) flow changes to irregular turbulent flow with eddies.

2. The equation of continuity, Av = constant, is a consequence of the conservation of

  1. A
    energy
  2. B
    momentum
  3. C
    angular momentum
  4. D
    mass
Show answer

Answer: D. For an incompressible fluid, the mass entering a tube of flow each second must equal the mass leaving it, so ρAv is constant.

3. When blood pressure is measured with a sphygmomanometer, the cuff is wrapped round the upper arm mainly because

  1. A
    the arteries of the arm are the largest in the body
  2. B
    blood flows fastest in the arm
  3. C
    the upper arm is at about the same level as the heart, so no correction for height is needed
  4. D
    there are no veins in the upper arm
Show answer

Answer: C. Pressure in a fluid changes with height (ρgh). Measuring at heart level gives the pressure the heart produces without a height correction.

4. A sphere of radius 1.0 mm moves at 0.020 m s−1 through water (η = 1.0 × 10−3 Pa s). The viscous drag on it is

  1. A
    1.2 × 10−7 N
  2. B
    1.9 × 10−7 N
  3. C
    3.8 × 10−4 N
  4. D
    3.8 × 10−7 N
Show answer

Answer: D. F = 6πηrv = 6π × 1.0 × 10−3 × 1.0 × 10−3 × 0.020 = 3.8 × 10−7 N. Leaving out π gives 1.2 × 10−7 N; not converting mm to m gives 3.8 × 10−4 N.

5. In a horizontal venturi meter carrying water, the speed in the wide part is negligible and the speed at the throat is 4.0 m s−1. The pressure difference between the wide part and the throat is

  1. A
    4 kPa
  2. B
    8 kPa
  3. C
    16 kPa
  4. D
    2 kPa
Show answer

Answer: B. Venturi relation: P1 − P2 = ½ρv22 = ½ × 1000 × 16 = 8000 Pa = 8 kPa. Leaving out the ½ gives 16 kPa.

6. Which of these liquids has the greatest viscosity at room temperature?

  1. A
    water
  2. B
    petrol
  3. C
    honey
  4. D
    alcohol
Show answer

Answer: C. Viscosity measures internal friction between layers of a fluid. Honey flows very slowly, so its viscosity is far greater than that of water, petrol or alcohol.

7. According to Stokes' law, if a sphere of twice the radius moves at the same speed through the same fluid, the drag force on it

  1. A
    doubles
  2. B
    halves
  3. C
    becomes four times as large
  4. D
    becomes eight times as large
Show answer

Answer: A. F = 6πηrv, so at the same speed F ∝ r. Doubling r doubles the drag.

8. A small steel ball falls through glycerine and reaches its terminal velocity. At this stage

  1. A
    the net force on it is zero
  2. B
    its acceleration equals g
  3. C
    the drag force on it is zero
  4. D
    its velocity starts to decrease
Show answer

Answer: A. At terminal velocity the upward drag (with upthrust) balances the weight, so the net force and the acceleration are zero and the speed stays constant.

9. Water flows at 2.0 m s−1 through a pipe of cross-sectional area 4.0 cm2 into a section of area 1.0 cm2. Its speed in the narrow section is

  1. A
    0.5 m s−1
  2. B
    8.0 m s−1
  3. C
    4.0 m s−1
  4. D
    2.0 m s−1
Show answer

Answer: B. A1v1 = A2v2: 4.0 × 2.0 = 1.0 × v2, so v2 = 8.0 m s−1. The fluid speeds up where the pipe narrows.

10. Which of these is NOT a property of an ideal fluid?

  1. A
    it is incompressible
  2. B
    it is non-viscous
  3. C
    its flow is steady
  4. D
    it experiences viscous drag in the pipe
Show answer

Answer: D. An ideal fluid is incompressible, non-viscous (no internal friction, so no viscous drag), and flows steadily without turbulence.

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Ways to practise this chapter

Fluid dynamics: questions students ask

How many Fluid dynamics MCQs are there?

21, each with the answer and a short explanation, across 2 topics: Viscous drag, Stokes' law and terminal velocity, Equation of continuity and Bernoulli's equation. Every chapter test draws ten of them, so you can take it many times.

Is the FSc Part 1 Physics chapter 6 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

Can I read the explanations in Urdu?

Yes. In practice mode and on your results you can switch the explanations to Urdu.

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