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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Specific Heat Capacities of Gases

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Specific Heat Capacities of Gases

An ideal gas sample ( γ = 1.5 ) is adiabatically compressed from a...

An ideal gas sample (γ=1.5\gamma = 1.5) is adiabatically compressed from a volume of 150 cm3150 \text{ cm}^3 to 50 cm350 \text{ cm}^3. The initial pressure and initial temperature are 150 kPa150 \text{ kPa} and 300 K300 \text{ K}. Determine the work done by the gas during this process.

Options

  1. A33 J33 \text{ J}
  2. B−33 J-33 \text{ J}
  3. C16.5 J16.5 \text{ J}
  4. D−16.5 J-16.5 \text{ J}

Correct answer

B. −33 J-33 \text{ J}

Step-by-step solution

Given P1=150 kPa=150×103 PaP_1 = 150 \text{ kPa} = 150 \times 10^3 \text{ Pa}, V1=150 cm3=150×10−6 m3V_1 = 150 \text{ cm}^3 = 150 \times 10^{-6} \text{ m}^3, V2=50 cm3=50×10−6 m3V_2 = 50 \text{ cm}^3 = 50 \times 10^{-6} \text{ m}^3, and γ=1.5\gamma = 1.5.

The work done by the gas in an adiabatic process is given by:

W=P1V1−P2V2γ−1W = \dfrac{P_1 V_1 - P_2 V_2}{\gamma - 1}

Using the adiabatic relation P1V1γ=P2V2γP_1 V_1^\gamma = P_2 V_2^\gamma, we can rewrite P2V2P_2 V_2 as P1V1(V1V2)γ−1P_1 V_1 \left(\dfrac{V_1}{V_2}\right)^{\gamma - 1}.

Substituting this into the work equation:

W=P1V1γ−1[1−(V1V2)γ−1]<br><br>Substitutingthegivenvalues:<br><br>W = \dfrac{P_1 V_1}{\gamma - 1} \left[1 - \left(\dfrac{V_1}{V_2}\right)^{\gamma - 1} \right]<br><br>Substituting the given values:<br><br>W = 150×103×150×10−61.5−1[1−(15050)1.5−1]\dfrac{150 \times 10^3 \times 150 \times 10^{-6}}{1.5 - 1} \left[1 - \left(\dfrac{150}{50}\right)^{1.5 - 1} \right]

W = \dfrac{22.5}{0.5} \left[1 - (3)^{0.5} \right]<br><br><br><br>W = 45 (1 - 3)<br><br>Using3≈\sqrt{3})<br><br>Using \sqrt{3} \approx1.732:<br><br>:<br><br>W = 45 (1 - 1.732) = 45 ×(−\times (-0.732) = -32.94  J<br><br>Roundingtothenearestinteger,\text{ J}<br><br>Rounding to the nearest integer,W ≈−\approx -33  J.\text{ J}.
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