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A plate of area `100 cm^(2)` is placed on the upper surface of castor oil, `2mm` thick. Taking the coefficient of viscosity to be `15.5` poise, calculate the horizontal force neccesary to move the plate with a velocity `3cm^(-1)`. |
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Answer» The (horizontal tangential) viscous force is given by `F=-etaA(dv)/(dy)` Given `eta=15.5` poise, `A=100cm^(2)` `(dv)/(dx)=(v_(2)-v_(1))/(x_(2)-x_(1))=((0-3)cm//s)/((2-0)mm) =-3//0.2=-15 s^(-1)` `F=15.5xx100xx(-15)=2.235xx10^(4)dyn=0.2325N` |
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