Mechanical Advantage of a Lever
Also known as law of the lever · class 1 lever
Worked example: 1.2 m effort arm, 0.3 m load arm → MA 4 — press Try an example to run it live, then adjust anything.
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Mechanical Advantage of a Lever explained
Balance the torques about a pivot, — and the force multiplication falls out as the ratio of the arms. A 1.2 m crowbar with its fulcrum 0.3 m from the load gives MA = 4, so 200 N of effort lifts 800 N. Archimedes summed it up around 250 BC with "give me a place to stand and I will move the Earth", and the three lever classes still classify tools today: a seesaw (class 1), a wheelbarrow (class 2), and tweezers or a human forearm (class 3, where MA is deliberately less than 1 to trade force for speed and range).
Nothing is free — the effort end must travel the same factor further, so a MA of 4 means moving your hand 4 cm to raise the load 1 cm, and the work in equals the work out. Real levers fall short of the ideal because friction at the pivot and flex in the bar eat a few percent, which is why the actual mechanical advantage measured from forces is always a little below this ideal value computed from lengths.
Mechanical Advantage of a Lever formula
- = Mechanical advantage
- = Effort arm length (m)
- = Load arm length (m)
Missing one of these? Work it out first, then come back
- Effort arm length — Torque, Torque with a Lever Arm (τ = rF sin θ)
- Load arm length — Torque, Torque with a Lever Arm (τ = rF sin θ)