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Work, energy and powerPhysicsHigh schoolabout 0:35

A motor does 9000 J of work in 30 s. What is its power?: animated lesson

A narrated, step-by-step work, energy and power video lesson with captions. Final answer: power P = 300 W.

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Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.2 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Worked example
A motor does 9000 J of work in 30 s. What is its power?
2. Step by step
1. $P = \frac{W}{t}$
  Formula: power
2. $P = (9000\ \text{J})\cdot (30\ \text{s})^{-1} = 300\ \text{W}$
  Substitute the known values
3. The answer
$\text{power P = 300 W}$
power P = 300 W
4. Check
- Substituted every value back into the formula: both sides agree ✓

Transcript

The problem. Here is the problem: A motor does 9000 J of work in 30 s. What is its power? Use the power formula, rearranged for the unknown, in SI units.

Step by step. Formula: power. Substitute the known values.

The answer. So the answer is power P equals 300 W. Power is the rate of doing work: one watt is one joule per second. The same work done in half the time needs twice the power.

Check. Substituted every value back into the formula: both sides agree, which checks out.

About work, energy and power

Work done by a force, kinetic and potential energy, and power.

A motor does 9000 J of work in 30 s. What is its power?