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ASVAB · Fluids and Hydraulics

Why does a heavy steel ship float while a small steel bolt sinks?

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Correct answer

The ship's shape displaces enough water to create buoyancy equal to its weight, while the dense bolt displaces little water

  1. A The ship is made of lighter steel
  2. B The ship's shape displaces enough water to create buoyancy equal to its weight, while the dense bolt displaces little water
  3. C Ships have no weight
  4. D The bolt is heavier than the ship

Why this is the answer

A steel SHIP floats because its hollow SHAPE DISPLACES a large volume of water, creating an upward BUOYANT FORCE equal to the ship's weight (Archimedes' principle); a solid steel BOLT displaces very little water, so its buoyant force is less than its weight, and it sinks. ASVAB Mechanical Comprehension tests buoyancy. BUOYANT FORCE = weight of displaced fluid; an object floats if it displaces water weighing as much as the object. The ship's shape (enclosing air, displacing much water) makes its average density less than water, while the compact bolt is denser. The buoyancy/displacement principle is commonly tested.
Source: ASVAB Mechanical Comprehension — Buoyancy

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About this topic: Fluids and Hydraulics

Fluids and hydraulics questions cover pressure (force ÷ area), Pascal's principle in hydraulic jacks and brakes, buoyancy, and how fluid speed and pressure change in pipes of different sizes. This is one of 13 Mechanical Comprehension questions on fluids and hydraulics, each with a full explanation on a single study page.

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