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11.Thermodynamics
medium
A litre of dry air at $STP$ expands adiabatically to a volume of $3$ litres. If $\gamma=1.40,$ the work done by air is$(3^{1.4}=4.6555)$ [Take air to be an ideal gas $]$
A
$90.5 \;J$
B
$48 \;J$
C
$60.7 \;J$
D
$100.8 \;J$
(JEE MAIN-2020)
Solution
$\mathrm{W}=\frac{\mathrm{nR}\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)}{\gamma-1}=\frac{\mathrm{P}_{1} \mathrm{V}_{1}-\mathrm{P}_{2} \mathrm{V}_{2}}{0.4}$
$W=\frac{100-\frac{100}{4.6555} \times 3}{0.4}=88.90\;J$
Standard 11
Physics
