Calculate Engine Efficiency: 0.490 kJ of Heat for 0.120 kJ of Work

AI Thread Summary
The engine releases 0.490 kJ of heat for every 0.120 kJ of work, leading to a calculation of efficiency. The correct formula for efficiency is the useful work divided by the total energy input. The total energy is the sum of the useful work and the waste heat generated. The correct calculation shows that efficiency is 0.120 kJ divided by the total energy of 0.450 kJ, resulting in an efficiency of approximately 0.211. Understanding the relationship between work output and heat input is crucial for accurate efficiency calculations.
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An engine releases 0.490 kJ of heat for every 0.120 kJ of work it does. What is the efficiency of the engine?

I am having trouble with this problem.
I tried

Wnet/ heat input = efficiency
0.120/0.450 = 0.27
but it says it is the wrong answer. (correct answer is 0.21)
 
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The efficiency is the useful work divided by the total energy. What is the total energy in terms of the useful work and the waste heat generated?
 
thanks!

0.120/(0.450+0.120) = 0.211
 

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