Answer :
Here the answer = 0.0080 .
Solution:
Based on stokes law,
v = g * D^2 *(d p - d m) / (18 V)
v = terminal velocity
D = diameter of particle
V = Viscosity
dp = density of particle
dm = density of medium.
Here density of ball = 1.42 gm/cc
By substituting,
v = 9.81 x 9.52 x 10^-3 ^2 (1420 - 1300) / 18 x 1.0
=5.92x10^-4
v(t) =0 .99 x Vtrm
=0 .99 x 0.0059
= 0.00059 m/s
v(t)/Vterm =1-e^(-t/r)
0.99 = 1 - e ^ (-t / 9.52 x 10^-3)
e ^ (-t / 9.52 x 10^-3) = 0.01
Taking log
-t / 9.52 x 10^-3 = -4.6
t = 0.0438 s
Then smaller ball
v = 9.81 x 2.38 x 10^-3 ^2 (1420 - 1300) / 18 x 1.0
= 0.000037 m/s
v(t) / Vterm = 1-e^(-t/r)
0.99 = 1 - e ^ (-t / 2.38 x 10^-3)
e ^ (-t / 2.38 x 10^-3) = 0.01
Taking log
-t / 2.38 x 10^-3 = -4.6
t = 0.0109 s
Here Reynolds number is,
R= rho vd / mu
= 1420 x 0.00059 x 9.52 x 10^-3 x / 1.0
= 0.0080
To learn more about stroke's law refer to :
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