OAR Mechanical Comprehension: Simple Machines 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 Comprehension: Simple Machines flashcards as text
A second-class lever always has a mechanical advantage:
Answer: Greater than 1
In a second-class lever the load is between the fulcrum and the effort, so the effort arm is always longer, giving MA > 1.
Two interlocking gears: Gear 1 has 20 teeth and Gear 2 has 5 teeth. If Gear 1 is the driver, the gear ratio is:
Answer: 0.25
Gear ratio (output/input) = teeth on driven gear / teeth on driver = 5/20 = 0.25, meaning the output spins faster.
Work input always equals work output in an ideal simple machine because:
Answer: Energy is conserved
In an ideal (frictionless) machine, the law of conservation of energy ensures work in equals work out.
A flagpole uses a pulley to raise a flag. This is an example of which pulley type?
Answer: Fixed pulley
A flagpole uses a fixed pulley, which changes the direction of force but provides no mechanical advantage.
If the efficiency of a machine is 80% and the work input is 500 J, what is the useful work output?
Answer: 400 J
Useful work output = efficiency × work input = 0.80 × 500 = 400 J.
A longer screwdriver handle (larger radius) makes a screw easier to turn because it:
Answer: Increases mechanical advantage
A larger handle radius increases the circumference swept per turn, increasing the mechanical advantage of the screw.
Which simple machine would be MOST useful for raising a heavy barrel into a truck bed?
Answer: Inclined plane (ramp)
An inclined plane (ramp) allows the barrel to be pushed up gradually, reducing the force needed compared to lifting straight up.