Mr. Franklin uses a machine that has an efficiency of 80%. The machine applies a force of 800 N through a distance of 20 m. Mr. Franklin applies a force of 50 N on the machine.Through what distance does Mr. Franklin apply the force?

The machine’s output work is 800 N × 20 m = 16,000 J. At 80% efficiency, this is 0.80 of the input work, so the input work is 16,000 ÷ 0.80 = 20,000 J. Mr. Franklin applies 50 N, so the distance is 20,000 J ÷ 50 N = 400 m. The correct choice is D, 400 m.

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