Mechanical Aptitude Mechanical Aptitude Levers, Pulleys, and Gears 5 — Questions and Answers
Question 1: A block-and-tackle system uses 3 movable pulleys and 3 fixed pulleys. What is the approximate mechanical advantage?
- 3
- 6 (Correct answer)
- 9
- 12
Correct answer: 6
The mechanical advantage of a block-and-tackle equals the number of rope segments supporting the load, which is 6 in this configuration.
Question 2: A crowbar being used to pry open a crate is what class of lever?
- First class (Correct answer)
- Second class
- Third class
- Pulley-lever hybrid
Correct answer: First class
A crowbar is a first-class lever: the fulcrum (edge of crate) is between the effort (your hands pushing down) and the load (lid being lifted).
Question 3: Gear A has 12 teeth and rotates at 600 RPM. If Gear B meshes with Gear A and rotates at 200 RPM, how many teeth does Gear B have?
- 4 teeth
- 18 teeth
- 36 teeth (Correct answer)
- 72 teeth
Correct answer: 36 teeth
Using the gear ratio formula: Teeth B = (RPM A × Teeth A) ÷ RPM B = (600 × 12) ÷ 200 = 36 teeth.
Question 4: In a gear train, the gear that receives power from the engine is called the:
- Driven gear
- Idler gear
- Driver gear (Correct answer)
- Output gear
Correct answer: Driver gear
The driver gear (also called the input gear) is the one connected to the power source and initiates motion in the gear train.
Question 5: What happens to torque when a small gear drives a larger gear?
- Torque decreases
- Torque stays the same
- Torque increases (Correct answer)
- Torque becomes zero
Correct answer: Torque increases
When a small driver gear turns a larger driven gear, speed decreases but torque increases proportionally (ignoring friction losses).
Question 6: A movable pulley is always attached to:
- The ceiling or support structure
- The load being lifted (Correct answer)
- The effort rope only
- The fixed pulley axle
Correct answer: The load being lifted
A movable pulley travels with the load, allowing two rope segments to share the weight and halving the required effort.
Question 7: Which statement correctly describes the trade-off when using a longer effort arm on a lever?
- Less effort is needed, but the effort must move a greater distance (Correct answer)
- Less effort is needed and the effort moves a shorter distance
- More effort is needed, but the load moves faster
- No trade-off exists — longer arms are always better
Correct answer: Less effort is needed, but the effort must move a greater distance
A longer effort arm reduces the force needed (higher MA) but requires the effort to travel a greater arc distance to move the load.
Mechanical Aptitude Mechanical Aptitude Levers, Pulleys, and Gears 5
A block-and-tackle system uses 3 movable pulleys and 3 fixed pulleys.
What is the approximate mechanical advantage?