Find the velocity of a bullet fired in standard air, if the Mach angle is 30°. For standard air R= 287 J/ Kg K, t= 15°C and k= 1.4

(04 Marks) Dec-2018

Subject Fluid Mechanics 2

Topic Compressible Flow

Difficulty Medium

Given : Mach angle $\alpha = 30˚$

R = 287 J/kg k

K = 1.4

Temperature t = 15˚ c

= 15 + 273 = 288˚ k

Now, Velocity of sound = $\sqrt {KRT}$

$= \sqrt {1.4 \times 287 \times 288}$

c = 340.17 m/s

Now, Mach angle,

Sin $\alpha = c/v$

i.e. Sin $30˚ = \frac{340.17}{V}$

$\therefore$ V = 680.34 m/s

$\therefore$ The velocity of a bullet fired in standard air is 680.34 m/s