Mechanical Advantage
Mechanical advantage is the factor by which a machine multiplies an input force. A machine with a mechanical advantage of 20 turns 50 kg of push into 1,000 kg of usable force — at the cost of the input having to move 20 times farther or faster than the output.
01Definition
Mechanical advantage is the factor by which a machine multiplies an input force. A machine with a mechanical advantage of 20 turns 50 kg of push into 1,000 kg of usable force — at the cost of the input having to move 20 times farther or faster than the output.
02Physical Principle
No machine creates energy; mechanical advantage only trades force against distance so that work in equals work out. A dragline's rigging, a forklift's hydraulic ram, and a bulldozer's final drive are all, underneath the steel, the same three-thousand-year-old idea as a crowbar under a rock — just reapplied through wire rope, oil pressure, or gear teeth instead of a wooden pole.
03Mathematical Foundation
04Interactive Diagram — Lever Mechanical Advantage
Slide the fulcrum position between a fixed effort and a fixed 500 kg load to see how mechanical advantage — and the effort actually needed — changes.
Load fixed at 500 kg. Moving the fulcrum toward the load shortens the load arm and raises mechanical advantage.
05Interesting Facts
- Archimedes is credited with the (probably apocryphal) claim that with a long enough lever and a place to stand, he could move the Earth — dimensionally, he wasn't wrong, only practically.
- A block-and-tackle pulley system used on cranes multiplies force by the number of rope segments supporting the load — count the strands to know the mechanical advantage.
- Every one of the twenty machines on this site owes at least one of its major systems to mechanical advantage: it is the most-cited concept in the whole encyclopedia.