Mechanical Advantage
Definition
How much a machine multiplies your force — a pulley system with mechanical advantage 4 lets you lift 400 N by pulling with only 100 N.
Technical definition
MA = F_out/F_in = d_in/d_out for an ideal machine. It follows from energy conservation: what you gain in force you pay for in distance.
Example
A 4 m ramp rising 1 m has MA ≈ 4 — pushing a 200 N crate up needs only about 50 N, ignoring friction.
Common confusion
Mechanical advantage is not free energy. A machine never delivers more work than you put in — real machines always deliver less, because friction takes its cut.