Between a plate of area `100 cm^(2)` and another plate of area `100 m^(2)` there is a `1 mm`, thick layer of water, if the coefficient of viscosity of water is `0.01` poise, then the force required to move the smaller plate with a velocity `10 cms^(-1)` with reference to large plate is

Options

A. ` 10 ^(-3) N `
B. `0.1 N `
C. ` 10 N `
D. ` 10 ^(4) N `

Answer

A

Explanation

Viscous force ` = |- eta A (dv)/(dx )| rArr F_(ext) = | - 0 .01 xx 100 xx (10)/(0.1) | = 100 dyne `
Hence to move with constant velocity ` F _ (ext ) ` must be equal to viscous force