Exam-style question
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A machine has a total input energy of 500 J and a useful output energy of 400 J. Calculate the efficiency of the machine.
- A.80%
- B.75%
- C.90%
- D.70%
Model answer
What a good answer should say
- 80%
Explanation
Why this works
Efficiency can be calculated using the formula efficiency = (useful output / total input) x 100. Substituting the values: efficiency = (400 J / 500 J) x 100 = 80%.
Therefore, the efficiency of the machine is 80%.
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