Problem Statement : - The vertical component of the landing speed of a parachute is 6m/s. consider parachute as an open hemisphere determine its diameter if the total weight to be carried is 1200 N.
Take mass density of air 1.205kg/m3 , CD =1.33.
Solution : -
$Given, $
$\ \ \ Cd = 1.33$
$\ \ \ Density = 1.205 Kg / m^3$
$\ \ \ Mass = 1200 N$
$\ \ \ Velocity= 6 m/sec$
With the parachute, neglecting buoyancy force using Newton’s second law of motion:
$$ \sum F = 0$$
$Therefore, $
$\implies mg - \frac{1}{2} \rho V^2 A C_d = 0$
$\implies 1500 - \frac{1}{2} \times 1.205 \times (6)^2 \times (\frac{\pi}{4}) D^2 \times 1.4 = 0$
$\implies 1500 = 0.6025 \times 36 \times (\frac{\pi}{4}) D^2 \times 1.4 $
$\implies 1500 \times 4 = 0.6025 \times 36 \times 3.14 \times D^2 \times 1.4$
$\implies 6000 = 95.34924 \times D^2$
$\implies D^2 = 62.92656$
$\implies D = 7.932626\ m$
So, therefore it's diameter will be 7.93 m. Ans.
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