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Mechanical Comprehension Flashcards

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

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  1. A firefighter needs to pry open a door using a halligan bar. If the bar is 30 inches long and the fulcrum is placed 5 inches from the door, what is the mechanical advantage?

    Answer: 5:1

    Mechanical advantage of a lever = effort arm / load arm = 25 inches / 5 inches = 5:1. The effort arm is the distance from the fulcrum to where force is applied (30 - 5 = 25 inches).

  2. Two gears are meshed together. Gear A has 40 teeth and Gear B has 20 teeth. If Gear A rotates at 100 RPM, how fast does Gear B rotate?

    Answer: 200 RPM

    When gears mesh, the gear ratio is inversely proportional to teeth count. Gear B speed = (Gear A teeth / Gear B teeth) × Gear A speed = (40/20) × 100 = 200 RPM.

  3. A pump system uses a pipe with a 4-inch diameter that narrows to a 2-inch diameter. According to the continuity equation, how does the water velocity change at the narrower section?

    Answer: Velocity quadruples

    By the continuity equation (A₁V₁ = A₂V₂), when the diameter halves, the cross-sectional area becomes one-quarter (area ∝ diameter²), so velocity must quadruple to maintain the same flow rate.

  4. A rope and pulley system uses three supporting ropes to lift a rescue basket. If the basket and patient weigh 300 pounds, approximately how much force must the rescuer apply (ignoring friction)?

    Answer: 100 pounds

    In an ideal pulley system with 3 supporting ropes, the force required equals the load divided by the number of supporting ropes: 300 / 3 = 100 pounds.

  5. A hydraulic jack has a small piston with an area of 2 square inches and a large piston with an area of 20 square inches. If 50 pounds of force is applied to the small piston, what force is generated at the large piston?

    Answer: 500 pounds

    Pascal's principle states that pressure is transmitted equally. Force₂ = Force₁ × (Area₂ / Area₁) = 50 × (20/2) = 500 pounds.

  6. An inclined plane (ramp) is 12 feet long and rises 3 feet in height. What is the mechanical advantage of this inclined plane?

    Answer: 4:1

    The mechanical advantage of an inclined plane = length / height = 12 / 3 = 4:1. This means the force needed to push a load up the ramp is one-quarter of lifting it straight up.