Types of motion and levers

Mechanisms change one kind of movement or force into another. The simplest mechanism of all is the lever.

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Four types of motion

Mechanisms use four types of motion:
MotionWhat it looks likeExample
LinearMoving in a straight line in one directionA paper trimmer blade sliding across
RotaryTurning round in a circleA wheel
ReciprocatingMoving backwards and forwards in a straight lineA sewing machine needle
OscillatingSwinging backwards and forwards in an arcA playground swing

Levers

A lever is a rigid bar that turns about a pivot called the fulcrum.
The force you put in is the effort. The force the lever moves is the load.
There are three classes of lever, depending on what is in the middle:
Class 1: fulcrum in the middle (see-saw, scissors, crowbar).
Class 2: load in the middle (wheelbarrow, nutcracker, bottle opener).
Class 3: effort in the middle (tweezers, fishing rod).

Mechanical advantage

Levers can make a small effort move a big load. Mechanical advantage = load ÷ effort.
If a lever lets an effort of 100 N lift a load of 400 N, the mechanical advantage is 400 ÷ 100 = 4.
The principle of moments says that for a balanced lever: effort × distance from fulcrum = load × distance from fulcrum.
So a long handle (effort far from the fulcrum) means less effort is needed.
Worked example

A crowbar has a fulcrum 0.2 m from a load of 600 N. The effort is applied 1.2 m from the fulcrum. What effort is needed to balance the load?

  1. Principle of moments: effort × effort distance = load × load distance.
  2. Effort × 1.2 = 600 × 0.2 = 120 N m.
  3. Effort = 120 ÷ 1.2 = 100 N.

Answer: 100 N.

Key idea

The four types of motion are linear, rotary, reciprocating and oscillating. A lever turns about a fulcrum; class 1 has the fulcrum in the middle, class 2 the load, class 3 the effort. Mechanical advantage = load ÷ effort.

Key words
Lever
A rigid bar that turns about a pivot (fulcrum), used to change the size or direction of a force.
Fulcrum
The pivot point that a lever turns about.
Mechanical advantage
Load ÷ effort. It shows how much a mechanism multiplies the force you put in.
Principle of moments
For a balanced lever: effort × distance from fulcrum = load × distance from fulcrum.

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2 more questions

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  1. A wheel turning round and round shows which type of motion?

    1. Linear
    2. Rotary
    3. Oscillating
    4. Reciprocating
    Show the answer

    Answer: Rotary

    Rotary means turning in a circle.

  2. A train travelling along a straight track shows which type of motion?

    1. Rotary
    2. Oscillating
    3. Linear
    4. Reciprocating
    Show the answer

    Answer: Linear

    Linear is a straight line in one direction.

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Last updated 2 October 2026. Spotted a mistake? Tell us and we will fix it.