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An ideal gas enclosed in a vertical cylindrical container supports a freely moving piston of mass M. The piston and the cylinder have cross sectional area A. When the piston is in equilibrium, the volume of the gas is V0 and its pressure is P0 . The piston is slightly displaced from the equilibrium position and released.Assuming that the system is completely isolated from its surrounding,the piston executes a simple harmonic motion with frequency:

 

  • Option 1)

    \frac{1}{2\pi }\sqrt{\frac{MV_{0}}{A\gamma P_{0}}}

  • Option 2)

    \frac{1}{2\pi }\, {\frac{A\gamma P_{0}}{V_{0}M}}

  • Option 3)

    \frac{1}{2\pi }\frac{V_{0}MP_{0}}{A^{2}\gamma }

  • Option 4)

    \frac{1}{2\pi }\sqrt{\frac{A^{2}\gamma P_{0}}{MV_{0}}}

 

Answers (1)

best_answer

As we have learned

Relation between slope of isothermal and adiabatic process -

\frac{dP}{dV}_{isothermal}= -\frac{P}{V}

\frac{dP}{dV}_{adiabatic}= -\gamma \frac{P}{V}

- wherein

Slope \, of \, adiabatic\, process = \gamma\, \times Slope \, of \, isothermal\, process

 

 

At equilibrium 

V = V_0 \; \; \; \; P = P_0

Let the atmospheric pressure is pa 

(P_0 - Pa )A =Mg ...........(1)

Let piston is displaced slightly into the cylinder then pressure become P_0 + dP

\Rightarrow Net \: \: \: force = Mg - (P_0 + dP )A +P_a A \\ = (Mg + P_a )A - P_0A - dP A

F = -dP A ...........(2)

Since cylinder is isolated , then the process is adiabatic \Rightarrow PV^r = constant

\Rightarrow dP = V^\gamma + pr v^{\gamma -1}dv = 0 \\ or\: \: dP = \frac{-\gamma P}{V }dV

\therefore F = - \frac{\gamma P_0}{V_0}A dV

dV + A dx \\ F = \frac{- P_0 \gamma A}{V_0 }Adx = \frac{- \gamma A^2P}{V_0 }dx

Acceleration = F/M = 

= \frac{- \gamma A^2P_0}{MV_0 }dx

This equation is of SHM with 

w^2 = \left ( \frac{\gamma P_0A^2}{MV_0 } \right )

T = 2 \pi \sqrt{\frac{MV_0}{\gamma P_0A^2 }}

= 1/T = \frac{1}{2\pi}\sqrt{\frac{\gamma P_0A^2}{MV_0}}

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Option 1)

\frac{1}{2\pi }\sqrt{\frac{MV_{0}}{A\gamma P_{0}}}

Option 2)

\frac{1}{2\pi }\, {\frac{A\gamma P_{0}}{V_{0}M}}

Option 3)

\frac{1}{2\pi }\frac{V_{0}MP_{0}}{A^{2}\gamma }

Option 4)

\frac{1}{2\pi }\sqrt{\frac{A^{2}\gamma P_{0}}{MV_{0}}}

Posted by

Avinash

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