WEBVTT

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Here is the problem: A 40 N force pulls a box 20 m at 0° to the direction of motion. How much work does it do?

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Use the work done by a constant force formula, rearranged for the unknown, in SI units.

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Formula: work done by a constant force.

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Substitute the known values.

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So the answer is work W equals 800 J.

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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.

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