THe velocity of sound in air at 16oC is 340ms-1. What will it be when the pressure is doubled and its temperature raised to 127ºC?
A
400 ms-1
B
4,000 ms-1
C
8,000 ms-1
D
160,000 ms-1
Verified Correct Answer: A.
Physical Principles & Numerical Solution
The velocity of sound in air, V∝\(\sqrt{T}\), where T is the absolute temperature
Thus V = K\(\sqrt{T}\) or K = \(\frac{\text{V}}{\sqrt{T}}\)
V is independent of pressure and density at a fixed temperature.
∴ \(\frac{V_1}{\sqrt{T_1}}\) = \(\frac{V_2}{\sqrt{T_2}}\)
T\(_1\) = 16 + 273 = 289K, V\(_1\) = 340ms\(^{-1}\)
T\(_2\) = 127 + 273 = 400K, V\(_2\) = ?
\(\frac{340}{\sqrt{289}}\) = \(\frac{V_2}{\sqrt{400}}\)
∴ V\(_2\) = \(\frac{340 \sqrt{400}}{\sqrt{289}}\) = 400m/s
Source: Myschool Past Questions Archive (Record #14510)