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# Power and Efficiency

## The percent of work put into by the user of a machine that becomes work done by the machine.

Levels are CK-12's student achievement levels.
Basic Students matched to this level have a partial mastery of prerequisite knowledge and skills fundamental for proficient work.
At Grade (Proficient) Students matched to this level have demonstrated competency over challenging subject matter, including subject matter knowledge, application of such knowledge to real-world situations, and analytical skills appropriate to subject matter.
Advanced Students matched to this level are ready for material that requires superior performance and mastery.

## Efficiency

Machines and friction, the efficiency of a machine and how to calculate it.

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## 동력과 효율

기계와 마찰, 기계의 효율과 그의 계산

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## Efficiency

Machines and friction, the efficiency of a machine and how to calculate it.

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## Efficiency

Machines and friction, the efficiency of a machine and how to calculate it.

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• Video

## Work, Power, and Efficiency: Sample Physics Problem

A worked through sample problem involving many important physics principals. Video courtesy of dcaulf.

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## Efficiency Quiz - MS PS

Reviews why all machines must overcome friction, how friction reduces the efficiency of machines, and how to calculate efficiency.

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