The internal energy change in a system that has absorbed 2 kCal of heat and done 500 J of work is:
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Question

The internal energy change in a system that has absorbed 2 kCal of heat and done 500 J of work is:

G1 Physics · Accepted Answer

Step 1: Use Q = ΔU + W (work done by system is positive). Step 2: Convert the absorbed heat: Q = 2 kcal = 2 × 1000 × 4.2 = 8400 J. Step 3: Work done by system: W = +500 J. Step 4: ΔU = Q − W = 8400 − 500 = 7900 J. Final answer: (D) 7900 J.