Fluid Mechanics Basics Quiz

Grade 11 · Science · Quiz

Apply your knowledge of pressure, buoyancy, fluid dynamics, and Bernoulli's principle to challenging problems.

Questions

  1. What is the gauge pressure at a depth of 10 m in freshwater (ρ = 1000 kg/m³, g = 9.8 m/s²)?

    1. 9.8 Pa
    2. 980 Pa
    3. 98000 Pa
    4. 9800000 Pa
    Show answer

    Answer: 98000 Pa

    Gauge pressure = ρgh = 1000 × 9.8 × 10 = 98,000 Pa (gauge pressure excludes atmospheric pressure).

  2. A hydraulic jack has a small piston of area 2 cm² and a large piston of area 100 cm². If a force of 50 N is applied to the small piston, what force is produced at the large piston?

    1. 1 N
    2. 250 N
    3. 2500 N
    4. 100 N
    Show answer

    Answer: 2500 N

    Pascal's principle: F1/A1 = F2/A2. F2 = F1 × (A2/A1) = 50 × (100/2) = 2500 N.

  3. An airplane wing generates lift primarily because:

    1. Air above the wing moves slower, creating higher pressure underneath
    2. Air above the wing moves faster, creating lower pressure above
    3. The wing is heavier than air
    4. The engine pushes air downward
    Show answer

    Answer: Air above the wing moves faster, creating lower pressure above

    Wing shape (airfoil) makes air travel faster over the curved top surface. By Bernoulli's equation, faster air = lower pressure above the wing; higher pressure below creates net upward lift.

  4. A steel ship floats even though steel is denser than water. This is because:

    1. Steel becomes less dense in seawater
    2. The ship's hull displaces enough water so the average density of the ship+air system is less than water
    3. Seawater is much denser than freshwater
    4. Surface tension holds the ship up
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    Answer: The ship's hull displaces enough water so the average density of the ship+air system is less than water

    A ship's hull is a large hollow structure. The average density of the entire ship (steel + trapped air) is less than water, so it displaces enough water weight to float.

  5. According to the continuity equation, if a river widens, water flow speed will:

    1. Increase
    2. Decrease
    3. Remain the same
    4. Reverse direction
    Show answer

    Answer: Decrease

    By the continuity equation A1v1 = A2v2, if cross-section A increases (river widens), velocity v must decrease to keep the flow rate constant.

  6. Bernoulli's equation assumes which of the following about the fluid?

    1. Compressible and viscous
    2. Incompressible and non-viscous
    3. Turbulent and fast-moving
    4. Dense and slow-moving
    Show answer

    Answer: Incompressible and non-viscous

    Bernoulli's equation applies to ideal fluid flow: incompressible (constant density), non-viscous (no friction), and steady (laminar) flow along streamlines.

  7. A submerged object experiences a greater buoyant force if it is pushed deeper into a uniform fluid.

    Show answer

    Answer: False

    Buoyant force depends only on the volume of fluid displaced (F_b = ρ_fluid·V_sub·g). For a fully submerged rigid object, V_sub doesn't change with depth, so F_b is constant regardless of depth.

  8. The SI unit of pressure is the _____, equivalent to one Newton per square meter.

    Show answer

    Answer: pascal

    The Pascal (Pa) is the SI unit of pressure: 1 Pa = 1 N/m². Named after Blaise Pascal who formulated the law of pressure transmission in fluids.

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