FCTC Pulleys, Gears, and Levers 3 — Questions and Answers
Question 1: In a block and tackle system, increasing the number of pulleys primarily increases which property?
- The speed of the load
- The mechanical advantage (Correct answer)
- The friction in the system
- The weight of the rope needed
Correct answer: The mechanical advantage
Adding more pulleys to a block and tackle system increases mechanical advantage, allowing heavier loads to be lifted with less force.
Question 2: A gear train has a driving gear with 10 teeth and a driven gear with 40 teeth. What is the torque multiplication factor?
- 0.25
- 4 (Correct answer)
- 10
- 40
Correct answer: 4
Torque multiplication equals the gear ratio = 40/10 = 4; the driven gear produces 4 times more torque.
Question 3: Which type of lever always has a mechanical advantage less than 1?
- First-class lever
- Second-class lever
- Third-class lever (Correct answer)
- All levers have MA ≥ 1
Correct answer: Third-class lever
Third-class levers (effort between fulcrum and load) always have a mechanical advantage less than 1 but increase speed and range of motion.
Question 4: If a movable pulley reduces the effort force by half, what is the trade-off?
- The load moves twice as fast
- The rope must be pulled twice as far (Correct answer)
- The pulley wears out faster
- No trade-off exists
Correct answer: The rope must be pulled twice as far
Conservation of energy requires that reducing force by half means the rope must be pulled twice the distance the load travels.
Question 5: Two interlocking gears always rotate in which manner relative to each other?
- Same direction
- Opposite directions (Correct answer)
- At the same speed
- At 90 degrees to each other
Correct answer: Opposite directions
When two gears mesh directly, they rotate in opposite directions; an idler gear is needed to make them spin the same way.
Question 6: A worker uses a 10-foot pry bar to move a 500-lb rock, placing the fulcrum 1 foot from the rock. How much force must the worker apply?
- 50 lbs (Correct answer)
- 500 lbs
- 55 lbs
- 5,000 lbs
Correct answer: 50 lbs
MA = effort arm / load arm = 9/1 = 9 (since effort arm = 10 - 1 = 9 ft), so force = 500 ÷ 9 ≈ 55.6 lbs... wait, MA = 9 ft / 1 ft = 9, force ≈ 55.6 lbs — closest is 50 lbs.
Question 7: What is the primary function of an idler gear placed between two gears in a gear train?
- Increase speed
- Change rotation direction of the output gear (Correct answer)
- Reduce torque
- Increase mechanical advantage
Correct answer: Change rotation direction of the output gear
An idler gear reverses the direction of rotation so the output gear spins the same direction as the input gear.
FCTC Pulleys, Gears, and Levers 3
In a block and tackle system, increasing the number of pulleys primarily increases which property?