A machine uses 2000 kJ of energy input and produces 500 kJ of useful energy. What is the efficiency?

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Multiple Choice

A machine uses 2000 kJ of energy input and produces 500 kJ of useful energy. What is the efficiency?

Efficiency shows how much of the input energy becomes useful energy. It’s found by dividing the useful energy by the total energy put in, then converting to a percentage. Here, useful energy is 500 kJ and input energy is 2000 kJ. So 500 ÷ 2000 = 0.25, which is 25%. The machine converts 25% of the input into useful work, while the rest is lost as waste heat or other losses. To see why the other numbers don’t fit: 1000 kJ would be 50%, 250 kJ would be 12.5%, and 1500 kJ would be 75%—none match the actual 500 kJ useful energy.

Efficiency shows how much of the input energy becomes useful energy. It’s found by dividing the useful energy by the total energy put in, then converting to a percentage.

Here, useful energy is 500 kJ and input energy is 2000 kJ. So 500 ÷ 2000 = 0.25, which is 25%. The machine converts 25% of the input into useful work, while the rest is lost as waste heat or other losses. To see why the other numbers don’t fit: 1000 kJ would be 50%, 250 kJ would be 12.5%, and 1500 kJ would be 75%—none match the actual 500 kJ useful energy.

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