Work and Power
Middle School
Definition
Work is the energy transferred when a force moves an object through a distance, measured in joules, while power is the rate at which that work is done, measured in watts. A more powerful machine does the same work in less time.
Worked examples
\(W = F \times d = 50\,\)N\( \times 10\,\)m\( = 500\,\)J\(\)
A 50-newton force pushing a box 10 meters does 500 joules of work.
\(P = \frac{W}{t} = \frac{500\,\)J\(}{5\,\)s\(} = 100\,\)W\(\)
If that 500 J of work is done in 5 seconds, the power output is 100 watts.
Common mistakes
- \(W = F \times d = 20\,\)N\( \times 0\,\)m\( = 20\,\)J\(\) → \(W = 20\,\)N\( \times 0\,\)m\( = 0\,\)J\(\) If the object doesn't move, no work is done—even if you push hard.
- A stronger machine always has more power. → Power depends on both work done and time taken. A weaker machine can have higher power if it completes the work faster.
- Power and energy are the same thing. → Power is the rate of energy transfer; energy is measured in joules, power in watts. 1 watt = 1 joule per second; power tells you how quickly energy is used.
Where you'll use it next
You'll apply work and power when analyzing machines, engines, and electrical circuits in physics, calculating mechanical advantage, efficiency, and energy consumption in engineering and everyday technology.
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026