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Work, energy and powerPhysicsHigh schoolabout 0:49

A 200 N force pulls a box 2.5 m at 30° to the direction of motion. How much work does it do?: animated lesson

A narrated, step-by-step work, energy and power video lesson with captions. Final answer: work W = 433.013 J.

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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 (0.3 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Worked example
A 200 N force pulls a box 2.5 m at 30° to the direction of motion. How much work does it do?
2. Step by step
1. $W = Fd\cos\theta$
  Formula: work done by a constant force
2. $W = \cos 30^\circ\,(200\ \text{N})\cdot (2.5\ \text{m}) = 433.013\ \text{J}$
  Substitute the known values
3. The answer
$\text{work W = 433.013 J}$
work W = 433.013 J
4. Check
- Substituted every value back into the formula: both sides agree ✓

Transcript

The problem. Here is the problem: A 200 N force pulls a box 2.5 m at 30° to the direction of motion. How much work does it do? Use the work done by a constant force formula, rearranged for the unknown, in SI units.

Step by step. Formula: work done by a constant force. Substitute the known values.

The answer. So the answer is work W equals 433.013 J. Only the component of the force along the displacement does work, hence the cos theta. Work is positive when the force has a component along the motion, negative when it opposes it (theta greater than 90°), and zero when it is perpendicular.

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 200 N force pulls a box 2.5 m at 30° to the direction of…