FCTC FCTC Mechanical Reasoning Principles Questions and Answers 5 — Questions and Answers
Question 1: A compound pulley system has 4 rope segments supporting the load. What is its mechanical advantage?
- 2
- 3
- 4 (Correct answer)
- 8
Correct answer: 4
In a pulley system, mechanical advantage equals the number of rope segments supporting the movable block, which is 4.
Question 2: An object weighing 80 lbs is placed on a frictionless inclined plane angled at 30°. What force parallel to the ramp is needed to hold the object in place?
- 20 lbs
- 40 lbs (Correct answer)
- 60 lbs
- 80 lbs
Correct answer: 40 lbs
The force needed equals weight × sin(30°) = 80 × 0.5 = 40 lbs.
Question 3: Gear A (8 teeth) drives Gear B (16 teeth), which is on the same shaft as Gear C (8 teeth), which drives Gear D (32 teeth). What is the overall gear ratio from A to D?
- 2:1
- 4:1
- 8:1 (Correct answer)
- 16:1
Correct answer: 8:1
Ratio A to B = 2:1; ratio C to D = 4:1; total ratio = 2 × 4 = 8:1 speed reduction.
Question 4: A refrigerator weighing 300 lbs is rolled up a 15-foot ramp to a platform 5 feet high. What is the ideal mechanical advantage of the ramp?
- 1.5
- 3 (Correct answer)
- 5
- 15
Correct answer: 3
MA = ramp length ÷ ramp height = 15 ÷ 5 = 3.
Question 5: What principle explains why a wider tire provides more traction on soft ground than a narrow tire of the same weight?
- Greater surface area reduces pressure per square inch (Correct answer)
- Greater surface area increases friction coefficient
- Wider tires generate more rolling resistance
- Wider tires increase the normal force on the ground
Correct answer: Greater surface area reduces pressure per square inch
Pressure = force ÷ area; spreading the same weight over a larger area reduces pressure per square inch, preventing the tire from sinking into soft terrain.
Question 6: A firefighter pulls a rope over a fixed pulley attached to the ceiling to raise a 180 lb victim. How much force must the firefighter exert on the rope (ignoring friction)?
- 60 lbs
- 90 lbs
- 180 lbs (Correct answer)
- 360 lbs
Correct answer: 180 lbs
A single fixed pulley only changes direction of force and provides no mechanical advantage, so the effort equals the load: 180 lbs.
Question 7: Two pistons in a hydraulic brake system: the master cylinder has a 1 sq in area and the caliper piston has a 4 sq in area. If the driver applies 25 lbs to the master piston, what clamping force is produced at the caliper?
- 6.25 lbs
- 25 lbs
- 50 lbs
- 100 lbs (Correct answer)
Correct answer: 100 lbs
Hydraulic pressure = 25 ÷ 1 = 25 psi; clamping force = 25 psi × 4 sq in = 100 lbs.
FCTC FCTC Mechanical Reasoning Principles Questions and Answers 5
A compound pulley system has 4 rope segments supporting the load.
What is its mechanical advantage?