Question detail
A machine has a useful energy output of 150 J and a total energy input of 200 J. What is its efficiency expressed as a percentage?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Conservation and dissipation of energy
Question
A machine has a useful energy output of 150 J and a total energy input of 200 J. What is its efficiency expressed as a percentage?
Answer
The efficiency is 75%. This is calculated using the formula: Efficiency (%) = (150 J / 200 J) x 100 = 75%.
Explanation
This question assesses the student's ability to apply the efficiency formula to a practical scenario, reinforcing their calculation skills in the context of energy transfers. This answer is linked to Efficiency because it applies the learning objective: Express efficiency as a percentage.. It shows the Physics relationship clearly and keeps energy, power, work done and efficiency terms distinct where they appear.
Common mistake
Confusing Efficiency Representation
Students often express efficiency as a decimal instead of a percentage, leading to incorrect answers.
To express efficiency as a percentage, multiply the decimal value by 100.
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