ASVAB (Armed Services Vocational Aptitude Battery)Mechanical Comprehension (MC)Easy
A worker uses a pulley system to lift a heavy crate. If the worker pulls 6 meters of rope to lift the crate 2 meters, what is the ideal mechanical advantage (IMA) of the pulley system?
- A12
- B2
- C0.33
- D3
Show answer & explanationAnswer & explanation
Correct answer: D. 3
The ideal mechanical advantage (IMA) of a pulley system is calculated by dividing the distance the effort force is applied (distance pulled by worker) by the distance the load is moved (distance the crate is lifted). IMA = Effort Distance / Load Distance = 6 meters / 2 meters = 3.
Why the other options are wrong
- A. Incorrect, a multiplication error.
- B. Incorrect, this would be if the distances were 4m and 2m.
- C. Incorrect, this is Load Distance / Effort Distance, which is the inverse of IMA.
Ideal Mechanical Advantage (IMA)
The theoretical mechanical advantage of a machine, calculated without considering friction or other energy losses. For pulleys, it's the ratio of the distance the effort moves to the distance the load moves.
- IMA = Effort Distance / Load Distance.
- Always greater than or equal to the actual mechanical advantage (AMA).
- For pulley systems, often equal to the number of rope segments supporting the movable pulley(s).
Memory trick: MA: More distance, Less force.