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Mechanical Aptitude Flashcards

7 cards from real NFST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Mechanical Aptitude flashcards as text

  1. A threaded bolt has 20 threads per inch. How far does the bolt advance into a nut with each full rotation?

    Answer: 0.05 inches

    Pitch = 1 / threads per inch = 1/20 = 0.05 inches of linear advance per full turn.

  2. When a fire hose is kinked, what happens to the water flow and pressure on the discharge side of the kink?

    Answer: Flow decreases and pressure behind the kink increases

    A kink acts like a restriction: flow downstream drops sharply while pressure builds up behind the kink on the supply side.

  3. Which of the following best explains why a larger diameter hose can deliver more water at the same pressure compared to a smaller hose?

    Answer: Larger hose has less friction loss per unit length

    Friction loss decreases dramatically as hose diameter increases, allowing greater volume flow at the same operating pressure.

  4. A reciprocating piston pump strokes 60 times per minute and displaces 0.5 gallons per stroke. What is its flow rate?

    Answer: 30 GPM

    Flow rate = Strokes per minute × Displacement per stroke = 60 × 0.5 = 30 GPM.

  5. What is the purpose of a pressure-reducing valve in a multi-story building's standpipe system?

    Answer: To prevent excessively high pressures on lower floors

    Lower floors in tall buildings experience very high static pressure; pressure-reducing valves limit outlet pressure to safe, usable levels for firefighting.

  6. Which of the following describes the mechanical principle behind a screw jack used to lift a vehicle?

    Answer: A rotating inclined plane (helix) converting rotational force to linear lifting force

    A screw is essentially a helical inclined plane; rotation applies force along the helix, converting torque into linear lifting force over a small distance.

  7. An air compressor tank is rated at 150 PSI maximum working pressure. A pressure gauge shows 140 PSI. If air continues to be pumped in, what safety device should activate next?

    Answer: The pressure relief valve opens

    When tank pressure reaches the set limit, the pressure relief valve opens to vent excess air, preventing a dangerous over-pressure condition.