OAR OAR Mechanical Comprehension: Simple Machines 4 โ Questions and Answers
Question 1: A second-class lever always has a mechanical advantage:
- Less than 1
- Equal to 1
- Greater than 1 (Correct answer)
- Equal to 0
Correct 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.
Question 2: Two interlocking gears: Gear 1 has 20 teeth and Gear 2 has 5 teeth. If Gear 1 is the driver, the gear ratio is:
- 0.25 (Correct answer)
- 4
- 1
- 15
Correct answer: 0.25
Gear ratio (output/input) = teeth on driven gear / teeth on driver = 5/20 = 0.25, meaning the output spins faster.
Question 3: Work input always equals work output in an ideal simple machine because:
- Friction is zero
- Energy is conserved (Correct answer)
- Force is always multiplied
- Speed is always reduced
Correct answer: Energy is conserved
In an ideal (frictionless) machine, the law of conservation of energy ensures work in equals work out.
Question 4: A flagpole uses a pulley to raise a flag. This is an example of which pulley type?
- Movable pulley
- Block and tackle
- Fixed pulley (Correct answer)
- Compound pulley
Correct answer: Fixed pulley
A flagpole uses a fixed pulley, which changes the direction of force but provides no mechanical advantage.
Question 5: If the efficiency of a machine is 80% and the work input is 500 J, what is the useful work output?
- 80 J
- 400 J (Correct answer)
- 420 J
- 500 J
Correct answer: 400 J
Useful work output = efficiency ร work input = 0.80 ร 500 = 400 J.
Question 6: A longer screwdriver handle (larger radius) makes a screw easier to turn because it:
- Reduces the pitch of the screw
- Increases mechanical advantage (Correct answer)
- Decreases the thread friction
- Shortens the travel distance
Correct answer: Increases mechanical advantage
A larger handle radius increases the circumference swept per turn, increasing the mechanical advantage of the screw.
Question 7: Which simple machine would be MOST useful for raising a heavy barrel into a truck bed?
- Wedge
- Fixed pulley
- Inclined plane (ramp) (Correct answer)
- Wheel and axle
Correct 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.
OAR OAR Mechanical Comprehension: Simple Machines 4
A second-class lever always has a mechanical advantage: