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ASVAB · Fluids and Hydraulics

A sharp knife cuts better than a dull one because the sharp edge:

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Correct answer

Concentrates the force over a smaller area, increasing pressure

  1. A Concentrates the force over a smaller area, increasing pressure
  2. B Is magnetic
  3. C Has less friction
  4. D Is heavier

Why this is the answer

A SHARP knife cuts better because its thin edge CONCENTRATES the force over a SMALLER AREA, increasing the PRESSURE. ASVAB Mechanical Comprehension tests pressure (PRESSURE = FORCE ÷ AREA). The same force applied over a smaller area produces greater pressure, allowing the blade to cut. A dull knife spreads the force over a larger area (lower pressure), so it cuts poorly. This is also why sharp points and edges (knives, needles, nails) work — small area, high pressure. The force/area/pressure relationship is commonly tested.
Source: ASVAB Mechanical Comprehension — Pressure and Area

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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.

New to this exam? Our ASVAB exam guide explains the format, scoring, and how to prepare.

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