The Lever

A lever is a simple machine consisting of a rigid bar pivoting on a fulcrum. It can multiply force or distance, depending on where the load, effort, and fulcrum are placed.

What Is a Lever?

A lever is a rigid bar that rotates around a fixed point called the fulcrum. By changing the position of the fulcrum, you can lift heavy loads with less effort.

A first-class lever with the fulcrum between the effort and the load.

The Moment (Torque)

A force applied at a distance from the fulcrum creates a turning effect called a moment.

Moment of a Force

M = F \times d

M = moment (N·m), F = force (N), d = perpendicular distance from fulcrum (m).

Lever Balance

A lever is balanced when the moments on both sides are equal:

$F_1 \times d_1 = F_2 \times d_2$

Classes of Lever

Class	Fulcrum position	Example
1st	Between effort and load	seesaw, scissors
2nd	Effort – Load – Fulcrum	wheelbarrow, nutcracker
3rd	Load – Effort – Fulcrum	tweezers, fishing rod

Tip In a first-class lever, a small effort far from the fulcrum can balance a large load close to the fulcrum.

A 60 N load sits 0.5 m from the fulcrum. How much effort is needed at 1.5 m from the fulcrum?

$F_1 \times d_1 = F_2 \times d_2$

$F_2 \times 1.5 = 60 \times 0.5$

$F_2 = \frac{30}{1.5} = 20 \text{ N}$

Real world: Scissors in everyday cutting

Scissors are a first-class lever — the pivot screw is the fulcrum, your hand applies the effort at the handles, and the material being cut is the load. Placing thick cardboard close to the fulcrum (near the pivot) makes cutting far easier because the mechanical advantage is greatest there.

Real world: Crowbar at a construction site

A construction worker uses a crowbar to pry out a nail. The edge of the crowbar rests on the surface as the fulcrum. With a long effort arm and a short load arm, even a large nail can be pulled out with surprisingly little force.

Real world: Wheelbarrow in the garden

A wheelbarrow is a second-class lever: the wheel is the fulcrum, the load (soil or bricks) sits in the tub (middle), and you lift the handles at the far end. A gardener can move 200 N of soil with an effort much less than 200 N.

Tip Where do you see this in real life? Look in your kitchen and garden — nutcrackers, bottle openers, brooms, and fishing rods are all levers!

Practice Problems

A lever has its fulcrum in the middle. A 40 N force is applied 2 m from the fulcrum. What load can be lifted 1 m from the fulcrum?

Show answer

F₁d₁ = F₂d₂ → 40×2 = F₂×1 → F₂ = 80 N.

Name two everyday examples of a 1st-class lever.

Show answer

Seesaw, scissors, crowbar, balance scale.