InterviewSolution
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InterviewSolution
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Spherical particles of pollen are shaken up in water and allowed to settle. The depth of water is `2xx10^(-2)m`. What is the diameter of the largest particles remaining in suspension one hour later? Density of pollen `=1.8xx10^(3)kgm^(-3)` viscosity of water `=1xx10^(-2)` poise and density of water `=1xx10^(-5)kgm^(-3)` |
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Answer» Terminal velocity `v=(2r^(2))/9 ((rho-sigma)g)/eta`…….i But we know `v=s/t` `:. s/t=2/9(r^(2)(rho-sigma)g)/etaimpliesr^(2)(9s)/(2t) eta/((rho-sigma)g)` Given `s=2xx10^(-2)m, t=1h=3600s` `:. Eta=1xx10^(-2)` poise `=1xx10^(-3)kgm^(-1)s^(-1)` Substituting given values we get `r^(2)=9/2xx(2xx10^(-2))/3600xx(1xx10^(-3))/((1.8xx10^(3)-1xx10^(3))xx10)=9/36xx1/810^(-10)` `=1/32xx10^(-10)` `:. r=sqrt(100/32)xx10^(-6)m=1.77xx10^(-6)m` Diameter `D=2r=2xx1.77mum=3.54mum` |
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