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Question 10

10.(a) If n identical water droplets falling under gravity with terminal velocity v collides to form a single drop which has the terminal velocity 4v, find the number n.

(b) If the velocity of water near the surface of a 6 m deep river is 6 m/s, assuming uniform velocity gradient along the depth, find the shear stress between the horizontal layers of water ( coefficient of viscosity of water = 10^{-2 }poise ).