Bill does 1500 J of work on a lever, which is a simple machine. The lever does 1350 J of work on a stone.What is the efficiency of the lever?

Efficiency is useful output work divided by input work, multiplied by 100%. The lever’s output is 1350 J and the input is 1500 J, so (1350 ÷ 1500) × 100% = 90%. Therefore, the lever’s efficiency is 90%, choice C.

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