Medium MCQ +4 / -1 PYQ · JEE Mains 2021

Two ideal polyatomic gases at temperatures T1 and T2 are mixed so that there is no loss of energy. If F1 and F2, m1 and m2, n1 and n2 be the degrees of freedom, masses, number of molecules of the first and second gas respectively, the temperature of mixture of these two gases is :

  1. A ${{{n_1}{F_1}{T_1} + {n_2}{F_2}{T_2}} \over {{F_1} + {F_2}}}$
  2. B ${{{n_1}{F_1}{T_1} + {n_2}{F_2}{T_2}} \over {{n_1}{F_1} + {n_2}{F_2}}}$ Correct answer
  3. C ${{{n_1}{T_1} + {n_2}{T_2}} \over {{n_1} + {n_2}}}$
  4. D ${{{n_1}{F_1}{T_1} + {n_2}{F_2}{T_2}} \over {{n_1} + {n_2}}}$

Solution

Initial internal energy = Final internal energy<br><br>$${{{F_1}} \over 2}{n_1}R{T_1} + {{{F_2}} \over 2}{n_2}R{T_2} = {{{F_1}} \over 2}{n_1}RT + {{{F_2}} \over 2}{n_2}RT$$<br><br>$\Rightarrow$ $T = {{{F_1}{n_1}{T_1} + {F_2}{n_2}{T_2}} \over {{F_1}{n_1} + {F_2}{n_2}}}$

About this question

Subject: Physics · Chapter: Thermodynamics · Topic: Zeroth and First Law

This question is part of PrepWiser's free JEE Main question bank. 271 more solved questions on Thermodynamics are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →