FAA Aviation Mechanic General (AMG)Physics, Math and Fluid LinesMedium
A technician rigs a block-and-tackle pulley system with 4 rope segments supporting the load to lift an engine weighing 800 pounds. Ignoring friction, what effort force is required at the free end of the rope?
- A200 lb
- B100 lb
- C3,200 lb
- D400 lb
Show answer & explanationAnswer & explanation
Correct answer: A. 200 lb
For a pulley system, mechanical advantage equals the number of rope segments supporting the load. Effort = Load / MA = 800 / 4 = 200 lb. The system trades force for distance, requiring the rope to be pulled 4 feet for every foot the load rises.
Why the other options are wrong
- B. This uses 8 segments, more than the system actually has.
- C. This multiplies instead of dividing the load by the MA.
- D. This uses only 2 segments instead of the actual 4.
Pulley Mechanical Advantage
In a block-and-tackle system, mechanical advantage equals the number of rope segments supporting the movable load, reducing the effort force needed.
- MA = number of supporting rope segments
- Effort = Load ÷ MA
- More supporting segments = less force but more rope pulled
Memory trick: 'Count the strands holding the weight' to find your force savings.