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NEET Physics QUESTION #1049
Question 1
Two gases A and B in cylinders with pistons of radius \(r_A\) and \(r_B\). Equal heat at constant pressure. Pistons move 16 cm and 9 cm. Internal energy change same. Ratio \(r_A/r_B\) is:
  • \(\dfrac{2}{\sqrt{3}}\)
  • \(\dfrac{\sqrt{3}}{2}\)
  • \(\dfrac{4}{3}\)✔️
  • \(\dfrac{3}{4}\)
Correct Answer Explanation
At constant pressure: \(Q = \Delta U + W\). Same \(\Delta U\) and same Q: so \(W_A=W_B\). Work done \(=p\cdot\pi r^2\cdot d\). So \(\pi r_A^2\cdot16 = \pi r_B^2\cdot9\Rightarrow\frac{r_A^2}{r_B^2}=\frac{9}{16}\Rightarrow\frac{r_A}{r_B}=\frac{3}{4}\).