Question

The speed of sound in a gas at S.T.P is $330m{s}^{-1}$ and the density of the gas is $1.3kg$ $m^{-3}$. The number of degrees of freedom of the gas is then

• A. 3
• B. 5
• C. 6
• D. 7

Answer 1

Answer: (B)

5

$S=1.3$ (density)

$\sqrt{\frac{\pi }{S}}=330$

$\sqrt{\frac{\pi }{S}}=330$

$\Rightarrow \frac{\pi }{S}=(330{)}^2$

$\Rightarrow \pi =(330{)}^2\times 1.3$

$\pi ={33}^2\times 130$

$=1.4$

$\frac{2}{f}+1=1.4$

$\Rightarrow \frac{2}{f}=0.4$

$\Rightarrow f=\frac{2\times 10}{4}$.