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Physics · PYQ NEET UG 2025
हिन्दीTwo gases \( A \) and \( B \) are filled at the same pressure in separate cylinders with movable pistons of radius \( r_A \) and \( r_B \), respectively. On supplying an equal amount of heat to both the systems reversibly under constant pressure, the pistons of gas \( A \) and \( B \) are displaced by \( 16\text{ cm} \) and \( 9\text{ cm} \), respectively. If the change in their internal energy is the same, then the ratio \( r_A / r_B \) is equal to
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Correct answer · Option B
\( \frac{3}{4} \)
Explanation
Since \( \Delta U = Q - P\Delta V \) is the same and \( Q \) is the same, \( P \Delta V_A = P \Delta V_B \implies \pi r_A^2 x_A = \pi r_B^2 x_B \implies r_A^2 (16) = r_B^2 (9) \implies \frac{r_A}{r_B} = \frac{3}{4} \).
