Engineering Board Exam Reviewer · Thermodynamics · medium
A paddle wheel does 200 kJ of work on a gas in a rigid tank while 50 kJ of heat is lost to the surroundings. What is the change in internal energy of the gas?
- 250 kJ
- −150 kJ
- 150 kJ
- 200 kJ
Answer
C. 150 kJ
Solution
W = -200 kJ (work input), Q = -50 kJ. U = Q - W = -50 + 200 = 150 kJ.
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