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FREE OAR Mechanical Reasoning Question and Answers Flashcards

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

Read the first 6 FREE OAR Mechanical Reasoning Question and Answers flashcards as text

  1. A hydraulic press has a small piston with an area of 2 sq in and a large piston with an area of 20 sq in. If a force of 15 lb is applied to the small piston, what force is exerted by the large piston?

    Answer: 150 lb

    By Pascal's principle, force is multiplied by the area ratio: 15 × (20/2) = 150 lb.

  2. Two meshing gears have 12 and 36 teeth respectively. If the smaller gear rotates at 900 RPM, what is the speed of the larger gear?

    Answer: 300 RPM

    Gear speed is inversely proportional to tooth count: 900 × (12/36) = 300 RPM.

  3. A 200-lb crate sits on a surface with a coefficient of static friction of 0.4. What minimum horizontal force is needed to start moving the crate?

    Answer: 80 lb

    Static friction force equals the coefficient times the normal force: 0.4 × 200 = 80 lb.

  4. In a first-class lever, the fulcrum is located 2 ft from the load and 6 ft from the effort. If the load weighs 150 lb, what effort is required to balance it?

    Answer: 50 lb

    By the lever principle, effort × effort arm = load × load arm, so effort = 150 × 2/6 = 50 lb.

  5. A block-and-tackle pulley system has 4 supporting ropes. Ignoring friction, what effort is needed to lift a 240-lb load?

    Answer: 60 lb

    The mechanical advantage equals the number of supporting ropes, so effort = 240/4 = 60 lb.

  6. A spring with a constant of 30 lb/in is compressed 4 inches. How much potential energy is stored in the spring?

    Answer: 240 in-lb

    Spring energy = ½kx² = ½ × 30 × 4² = 240 in-lb.