Exam-style question
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A heat engine receives 5000 J of energy input and does 2000 J of useful work. What is the efficiency of the engine?.
- A.40%
- B.50%
- C.60%
- D.70%
Model answer
What a good answer should say
- 40%
Explanation
Why this works
The efficiency is calculated as the useful work output divided by the total energy input, multiplied by 100. Here, the initial values are 2000 J (useful work) and 5000 J (energy input).
The calculation shows that the efficiency is 40%.
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