GATE 2020 ME (ME2) – Question 62
Air is in the shown frictionless piston-cylinder. Atmospheric pressure is 100 kPa, initial air pressure 105 kPa and piston area 300 cm². Heat is added and the piston rises slowly to its stops. Spring constant is 12.5 N/mm. Find work interaction for the air system (J), nearest integer.
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Correct answer: 543 to 545
Explanation
Baseline pressure accounts for atmosphere and piston weight. Its work is105000×0.03×0.16=504 J. Spring compression is0.08 m,adding(1/2)(12500)(0.08²)=40 J. Total boundary work is **544 J**. Applying spring resistance over the initial clearance would overestimate the work.