Work & Energy
Push, pull, lift or drag — whenever a force moves something, it does work and transfers energy. Master W = F × s, the joule, and why friction always warms things up.
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Work & Energy ⚙️
In physics, **work** has an exact meaning: work is done whenever a **force moves an object**. Doing work **transfers energy** — the work done equals the energy transferred. Lift a box, drag a sledge, stretch a spring — in each case a force does work.
Work done 💪
The work done by a force is: **W = F s** (work = force × distance moved along the line of the force). Work is in **joules (J)**, force in **newtons (N)**, distance in **metres (m)**. The distance must be measured **in the direction of the force**.
Work out the work done
An interactive activity.
Order the method
An interactive activity.
The joule 📏
The **joule** is the unit of both work and energy — because doing work IS transferring energy. One joule is the work done when a force of **1 newton** moves an object **1 metre**. In other words, **1 J = 1 N·m**.
One joule
Work done is measured in joules. One joule is the work done when...?
- A force of 1 newton moves an object 1 metre
- A mass of 1 kilogram is lifted
- 1 amp of current flows for 1 second
- 1 watt is used for 1 hour
Working against friction 🔥
When you do work **against friction**, the energy transferred does not go anywhere useful — it is transferred to the **thermal store** of the object and surroundings. That is why rubbing your hands together warms them up, and why brakes get hot. The work done against friction heats things up.
Find the distance
An interactive activity.
Match each quantity to its unit
- Work done
- Force
- Distance
- Power
- Joule (J)
- Newton (N)
- Metre (m)
- Watt (W)
The work rules
Work done equals the energy _____. It is calculated with work = force × _____, and measured in _____. Work done against friction is transferred to the thermal store, heating things up.