medium difficulty6 min

Simple Machines — Pulley, Inclined Plane, Lever

Simple machines are basic devices that make work easier by changing the size of force, direction of force, or distance over which force is applied.

In one line: Machines trade force with distance or direction.

Practice This Concept

Understand it

A pulley can change the direction of effort or reduce effort in a system.
An inclined plane reduces the force needed to raise a load by increasing the distance moved.
A lever helps lift or move loads using a fulcrum, effort, and load.
These machines do not remove work; they trade force and distance.

Example

A ramp helps push a heavy box into a truck using less force over a longer distance.

Rule to remember

Mechanical advantage = load/effort.

In ideal machines, work input is approximately equal to work output, but real machines lose some energy due to friction.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

A ramp of longer length needs less force than direct lifting for the same height, but the object must be moved through a greater distance.

Method you can reuse

Identify the machine, mark load and effort, locate fulcrum if it is a lever, decide whether force or direction changes, and relate it to distance moved.

Sketch it in your answer

Draw labelled diagrams of a pulley with load and effort, an inclined plane with height and length, and a lever with fulcrum, load, and effort.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why is it easier to push a load up a ramp than lift it straight up?

Think first, then show answer

It is easier because the ramp increases the distance over which effort is applied, so the required force becomes smaller, though the ideal work remains the same.

Common wrong answer

Saying a pulley reduces the weight of the load is wrong; it may reduce required effort in a system or change direction, but the load's weight remains the same.

Don't mix this up

Students often think a simple machine creates extra energy, but it only helps use force more conveniently.

Exam tip

In explanation questions, write what changes: force, distance, or direction. Do not say the machine creates work.