First, Second & Third Class Levers

This lesson covers levers — one of the simplest and most important mechanisms. You must understand the three classes of lever and be able to calculate mechanical advantage for AQA GCSE Design and Technology (8552), Section 3.1.5.

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What Is a Lever?

A lever is a rigid bar that pivots around a fixed point called the fulcrum (or pivot). A lever is used to:

• Multiply force (make it easier to lift heavy loads)
• Multiply distance/speed (make small movements into large ones)
• Change the direction of a force

Key Terms

Term	Definition
Fulcrum (F)	The fixed pivot point around which the lever rotates
Effort (E)	The input force applied by the user
Load (L)	The output force or resistance that needs to be overcome
Effort arm	The distance from the effort to the fulcrum
Load arm	The distance from the load to the fulcrum

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First Class Lever

In a first class lever, the fulcrum is between the effort and the load.

Arrangement: Effort — Fulcrum — Load (E-F-L)

Examples of First Class Levers

Example	Effort	Fulcrum	Load
Seesaw	Person sitting on one end	Central pivot	Person sitting on the other end
Scissors	Hand squeezing the handles	The screw/rivet joining the blades	Material being cut
Crowbar	Hand pushing down on the long end	Stone or block under the bar	Nail or object being levered up
Pliers	Hand squeezing the handles	The pivot joint	Object being gripped
Claw hammer (removing nails)	Hand pulling the handle	Head resting on the wood surface	Nail being pulled out

Properties of First Class Levers

• The effort and load move in opposite directions.
• Can provide mechanical advantage (force multiplication) if the effort arm is longer than the load arm.
• Can also provide speed/distance advantage if the load arm is longer (but force is reduced).

AQA Exam Tip: First class levers are the only class where the effort and load move in opposite directions. This is a key identifying feature in exam diagrams.

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Second Class Lever

In a second class lever, the load is between the fulcrum and the effort.

Arrangement: Fulcrum — Load — Effort (F-L-E)

Examples of Second Class Levers

Example	Effort	Fulcrum	Load
Wheelbarrow	Hands lifting the handles	The wheel (axle)	The load in the barrow
Nutcracker	Hand squeezing the handles	The hinge at one end	The nut being cracked
Bottle opener	Hand pulling up on the handle	The lip of the bottle cap	The cap being removed
Door (pushing)	Hand pushing the handle (far from hinges)	The hinges	The weight of the door
Stapler	Hand pressing down on the top	The hinge at the back	The staple being pushed through paper

Properties of Second Class Levers

• The effort arm is always longer than the load arm.
• This means second class levers always multiply force (MA > 1).
• The trade-off is that the effort moves a greater distance than the load.
• Effort and load move in the same direction.

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Third Class Lever

In a third class lever, the effort is between the fulcrum and the load.

Arrangement: Fulcrum — Effort — Load (F-E-L)

Examples of Third Class Levers

Example	Effort	Fulcrum	Load
Tweezers	Fingers squeezing in the middle	The joined end	The tips gripping an object
Fishing rod	Hand holding the rod (near the handle)	The butt end (base)	The fish on the line (tip)
Human forearm	Biceps muscle pulling on the forearm (near the elbow)	Elbow joint	The hand holding a weight
Broom / sweeping	Hand in the middle of the handle	Bottom hand (fulcrum)	The broom head
Cricket bat / tennis racket	Hands gripping near the handle	Wrist/base of handle	The head/face of the racket
Tongs	Hand squeezing near the pivot	The pivot/hinge	The tips gripping food

Properties of Third Class Levers

• The effort arm is always shorter than the load arm.
• This means third class levers always multiply distance and speed (MA < 1).
• The trade-off is that the effort must be greater than the load.
• Effort and load move in the same direction.

AQA Exam Tip: A common way to remember the three classes: "FLE 1-2-3". First class: F between L and E. Second class: L between F and E. Third class: E between F and L.

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Mechanical Advantage (MA)

Mechanical advantage tells you how much a lever multiplies the input force.

Formula

$MA = \frac{\text{Load}}{\text{Effort}} = \frac{\text{Effort arm length}}{\text{Load arm length}}$MA=EffortLoad​=Load arm lengthEffort arm length​

Worked Examples

Example 1: A crowbar (first class lever) is used to pry up a rock. The effort arm is 1.2 m and the load arm is 0.3 m.

$MA = \frac{1.2}{0.3} = 4$MA=0.31.2​=4

This means the crowbar multiplies the input force by 4 times. If you apply 50 N of effort, you can lift a 200 N load.

Example 2: A wheelbarrow (second class lever) has an effort arm of 1.5 m and a load arm of 0.5 m.

$MA = \frac{1.5}{0.5} = 3$MA=0.51.5​=3

The wheelbarrow multiplies force by 3. To lift a 300 N load, you only need 100 N of effort.

Example 3: A fishing rod (third class lever) has an effort arm of 0.4 m and a load arm of 2.0 m.

$MA = \frac{0.4}{2.0} = 0.2$MA=2.00.4​=0.2

The MA is less than 1, meaning the rod does not multiply force. Instead, it multiplies distance and speed — a small movement of the hand produces a large movement of the rod tip. You need 5 times more effort than the load.

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Comparing the Three Classes

The diagram below shows the arrangement of Effort (E), Fulcrum (F) and Load (L) for each lever class:

graph TD
    subgraph "**1st Class** — e.g. Seesaw"
        A1["Effort ⬇"] --- B1["===== Fulcrum ⚖ ====="] --- C1["Load ⬆"]
    end
    subgraph "**2nd Class** — e.g. Wheelbarrow"
        A2["Fulcrum ⚖"] --- B2["===== Load ⬇ ====="] --- C2["Effort ⬆"]
    end
    subgraph "**3rd Class** — e.g. Tweezers"
        A3["Fulcrum ⚖"] --- B3["===== Effort ⬆ ====="] --- C3["Load ⬇"]
    end