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OAR Mechanical Reasoning Flashcards

7 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 7 OAR Mechanical Reasoning flashcards as text

  1. A lever is 10 feet long with the fulcrum 2 feet from the load end. If a 400 lb load is placed on the short end, how much force is needed on the long end to balance it?

    Answer: 100 lb

    Using the lever principle: 400 × 2 = F × 8, so F = 100 lb.

  2. Water flows through a pipe that narrows from 4 inches in diameter to 2 inches. Compared to the wide section, the water speed in the narrow section is:

    Answer: Four times as fast

    Flow rate is constant; halving the diameter quarters the area, so speed quadruples.

  3. A block sits on a ramp inclined at 30°. The component of gravity acting parallel to the ramp surface (pulling the block down the slope) equals:

    Answer: mg × sin30°

    The component of gravity along an incline is mg × sinθ.

  4. Two gears mesh together. Gear A has 12 teeth and Gear B has 36 teeth. If Gear A turns at 180 RPM, what is the speed of Gear B?

    Answer: 60 RPM

    Gear ratio = 12/36 = 1/3, so Gear B turns at 180 × (1/3) = 60 RPM.

  5. A spring with a spring constant of 50 N/m is compressed 0.4 m from its natural length. How much potential energy is stored in the spring?

    Answer: 4 J

    Elastic potential energy = ½kx² = ½ × 50 × 0.16 = 4 J.

  6. Which type of wrench provides the greatest mechanical advantage when loosening a very tight bolt?

    Answer: A long breaker bar

    A longer handle increases the torque (force × distance) applied to the bolt.

  7. A hydraulic jack has an input piston with area 2 in² and an output piston with area 20 in². If 50 lb of force is applied to the input, what load can the output lift?

    Answer: 500 lb

    Pressure is equal throughout: F_out = F_in × (A_out/A_in) = 50 × 10 = 500 lb.