A metal plate 100`cm^2` in area rests horizontally on a layer of oil 2 mm thick.A force of 0.1 N applied to the plate horizontally keeps it moving with a uniform speed of 2cm/s . Find the viscosity of oil.

Explanation

Since the metal plate is moving uniformly the applied force just overcomes the drag
From F = `eta A (dv)/(dy), eta = (F)/(A(dv)/(dy))` = `(0.1)/(100 xx 10^-4) xx (2 xx 10^-2)/(2 xx 10^-3) = 1Ns/m^2`