Question

A circular metal plate of radius 6 cm rests on a layer of caster oil 1.5 mm thick, whose coefficient of viscosity is 15.5 poise. Find the horizontal force (in kg wt) required to move the plate with a speed of `60 ms^(-1)`.

Answer 1

Here, `r= 6 cm`
`dx = 1.5 mm = 0.15 cm , eta = 15.5 poise`
`d upsilon = 6 cm s^(-1), A = pi r^(2) = 22/7 xx (6)^(2) cm^(2)`
`= 7xx10^(4) dyn e`
`=(7 xx 10^(4))/(980) g wt = ( 7xx10^(4))/(980xx1000)kg wt`
`=0.071 kg wt`.