An air bubble of diameter 4mm rises steadily through a solution of density 1800kg/m3 at the rate of 0.05m/s. Neglecting density of air, the co-efficient of viscosity of the solution is [Take g=10m/s2]
A
0.64poise
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B
6.4poise
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C
0.32poise
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D
3.2poise
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Solution
The correct option is D3.2poise Given, diameter of air bubble, d=4mm Radius of air bubble, r=2mm=2×10−3m Density of solution, ρ=1800kg/m3 Speed of air bubble, v=0.05m/s Co-efficient of viscosity of solution, η=? As air bubble rises steadily, therefore net force on it should be zero. Also, density of the air is neglegile, so we can neglect force due to gravity.