Physics - Mechanics

Leverage (The Law of the Lever) Explained Simply

A lever is a bar that rotates around a fixed point (the pivot). With a lever, you can move a heavy load with little force - if you push on the right side, far enough from the pivot.

F₁ · l₁ = F₂ · l₂ force times force-arm = load times load-arm
Load Force Pivot

Short arm to the heavy load, long arm to the force - that's how a little force moves a lot of load.

đź’¬ Mia asks Grandpa Theo

Mia

Why can I lift a much heavier dad on a seesaw if I sit far out at the end?

Grandpa Theo

Because your distance to the pivot is greater! Your force gets multiplied by your long lever arm - the further out you sit, the more "punch" your weight has.

Mia

Can you work through an example for me?

Grandpa Theo

Sure! A load of 600 newtons sits 1 meter from the pivot. You sit 3 meters away. How much force do you need? 600 · 1 = F · 3, so F = 200 newtons - a third of the load!

This principle is also behind nail clippers, scissors, nutcrackers, and crowbars - anywhere a small force needs to achieve a big effect.

Fun Fact

The Greek scholar Archimedes is said to have declared about the lever: “Give me a place to stand, and I shall move the Earth.” That is exactly what he meant - with a long enough lever and a fixed pivot point, you could in theory move the entire planet.

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