---
title: "Calculating Work Done and Power"
description: "Work done is force times the distance moved along the force, measured in joules, and power is the work done each second, measured in watts. For steady motion the two combine as power equals force time"
canonical: https://lightmysky.com/learn/science/calculating-work-done-and-power-mt_udulQxseg1
source: https://lightmysky.com/learn/science/calculating-work-done-and-power-mt_udulQxseg1.md
retrieved: 2026-09-12
---

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# Calculating Work Done and Power

Work done is force times the distance moved along the force, measured in joules, and power is the work done each second, measured in watts. For steady motion the two combine as power equals force times speed.

Subject: Science · Area: Energy · Ages 15 to 16
Page: https://lightmysky.com/learn/science/calculating-work-done-and-power-mt_udulQxseg1

## Ready when they can

- Calculates work done when a force drags, lifts or pushes something a stated distance
- Converts between joules, watts and seconds to find any missing quantity
- Explains why carrying a bag horizontally does no work against the lifting force

## Lesson: Push along, and count the joules

Work has a strict scientific meaning for you: force times distance moved along that force, in joules. Push a wall all day with no movement and you do zero work, however tired you feel. Only the distance along the force counts.

**Example.** Carrying a shopping bag along a flat corridor does no work against the lifting force, because the motion runs sideways to the upward pull. Lift the same bag up the stairs and it counts, since the movement follows the force.

Power tells you how fast work gets done: power = work divided by time, in watts, and one watt is one joule per second. A motor lifting a 40 kg crate 3 m in 5 s: weight 400 N, work 400 times 3 = 1200 J, power 1200 divided by 5 = 240 W. Cover and rearrange to find any missing quantity.

**Tip.** Juggling joules, watts, and seconds is one equation in three outfits. Write units at every step: newtons times metres give joules, joules divided by seconds give watts. The units check the maths for you.

**Recap.** Force along the distance makes joules, joules per second make watts.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Impulse and Crash Safety](https://lightmysky.com/learn/science/impulse-and-crash-safety-mt_BjLAFw2zjU)
- [Power: watts and energy per second](https://lightmysky.com/learn/science/power-watts-and-energy-per-second-mt_ckpA3oZQ44)
- [Efficiency, Sankey diagrams, and work done](https://lightmysky.com/learn/science/efficiency-sankey-diagrams-and-work-done-mt_JyfLtl_nhw)

## Opens up

- [Gravitational Potential and Escape Speed](https://lightmysky.com/learn/science/gravitational-potential-and-escape-speed-mt_drqTwCD9W8)
- [Stopping Distances and Braking Energy](https://lightmysky.com/learn/science/stopping-distances-and-braking-energy-mt_nRNZS4jHoj)
- [Work Done by a Force at an Angle](https://lightmysky.com/learn/science/work-done-by-a-force-at-an-angle-mt_OvBtur6dW5)
- [Kinetic and Gravitational Potential Stores](https://lightmysky.com/learn/science/kinetic-and-gravitational-potential-stores-mt_uD3jklaZCw)