Learning objectives
- Distinguish fixed and moving pulleys.
- Count supporting rope sections.
- Calculate ideal and actual mechanical advantage.
- Connect effort, rope travel and work.
Equations
Load = mg. IMA = n. Actual MA = ηn. Effort = mg/(ηn). Input travel = n × load rise. Wout = mg × rise. Win = Wout/η.
Model assumptions
The rope does not stretch. Wheels and rope are massless. Motion is slow and steady; the operator supplies the required effort. Efficiency is a lumped loss factor. Equal tension is used only as an ideal reference, not as a detailed friction model.
Only rope sections supporting the moving load count toward n. A fixed wheel used to redirect the pull does not automatically increase n. Short rope markers help show motion; their repeating pattern is a visual aid.