SSC JE Civil Engineering 2018 Set 3 Solved Paper

Question : 144 of 200

Marks: +1, -0

The sphere of diameter 0.02 m is falls in the fluid of kinematic viscosity 10 stokes with the terminal velocity of 0.02 m/s. What is the value of coefficient of drag on the falling sphere?

Validate

Solution:

v_s=[{4/3 gd(G-1)}/c_D]^{1/2}

v_s

= Terminal velocity = 0.02 m/sec
d = 0.02m = diameter of particle.
ν kinematic viscosity = 10 stokes = 10 × 10

^{–2}

m/sec

[v_s=g/18(G-1)d^2/\ν]

[R_e={ ρVD}/M]

R_e={VD}/\ν={0.02 -0.02}/{10×10^{-4}}=0.4

C_D=24/ R_e=24/0.4=60

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