Mechanical Aptitude Mechanical Aptitude Levers, Pulleys, and Gears 3 — Questions and Answers
Question 1: Three gears are in a line: A drives B, B drives C. If A and C have 30 teeth and B has 15 teeth, which direction does C rotate compared to A?
- Opposite direction
- Same direction (Correct answer)
- C does not rotate
- Perpendicular direction
Correct answer: Same direction
With an odd number of meshed gears in a line, the first and last gears rotate in the same direction; the middle gear is an idler.
Question 2: A movable pulley is attached to the load. How does this affect the effort required to lift the load?
- Doubles the effort needed
- Has no effect on effort
- Halves the effort needed (Correct answer)
- Triples the effort needed
Correct answer: Halves the effort needed
A single movable pulley provides a mechanical advantage of 2, meaning you only need half the force to lift the load.
Question 3: A seesaw with two children is balanced. Child A (60 lbs) sits 4 feet from the fulcrum. Where must Child B (80 lbs) sit to maintain balance?
- 4 feet from fulcrum
- 3 feet from fulcrum (Correct answer)
- 5 feet from fulcrum
- 6 feet from fulcrum
Correct answer: 3 feet from fulcrum
For balance, torques must be equal: 60 × 4 = 80 × d, so d = 240 ÷ 80 = 3 feet.
Question 4: Which type of gear is used to transmit power between shafts at a 90-degree angle?
- Spur gears
- Helical gears
- Bevel gears (Correct answer)
- Rack and pinion
Correct answer: Bevel gears
Bevel gears have angled teeth cut on a conical surface, making them ideal for transmitting rotation between perpendicular shafts.
Question 5: In a block-and-tackle system, increasing the number of pulleys primarily:
- Increases the distance through which effort must be applied (Correct answer)
- Decreases the total weight lifted
- Increases the speed of lifting
- Has no effect on effort
Correct answer: Increases the distance through which effort must be applied
Greater mechanical advantage means less force is needed, but the effort rope must be pulled a proportionally greater distance.
Question 6: A lever has a mechanical advantage of 5. If the load weighs 200 pounds, how much effort is required (ignoring friction)?
- 1,000 lbs
- 200 lbs
- 40 lbs (Correct answer)
- 100 lbs
Correct answer: 40 lbs
Effort = Load ÷ Mechanical Advantage = 200 ÷ 5 = 40 lbs.
Question 7: A rack-and-pinion gear system converts:
- Rotational motion to linear motion (Correct answer)
- Linear motion to rotational motion only
- Speed to torque without motion change
- Vertical motion to horizontal motion
Correct answer: Rotational motion to linear motion
A rack-and-pinion converts the pinion gear's rotational motion into the straight-line (linear) motion of the rack.
Mechanical Aptitude Mechanical Aptitude Levers, Pulleys, and Gears 3
Three gears are in a line: A drives B, B drives C.
If A and C have 30 teeth and B has 15 teeth, which direction does C rotate compared to A?