Exam-style question
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A machine uses 2000 J of energy to perform work, but 300 J is lost as heat. What is the useful work done by the machine?.
Model answer
What a good answer should say
- The useful work done by the machine is 1700 J.
Explanation
Why this works
This question assesses the understanding of energy transfer and work done. The useful work is calculated by subtracting the energy lost from the total energy input.
Thus, useful work = total energy - energy lost = 2000 J - 300 J = 1700 J. This shows the ability to apply the concept of energy transfer in a practical scenario.
Common mistake
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