A metel plate 100 sq cm in area rests on a 2-mm layer of castor oil, whose coefficient of viscosity is `1.55` SI units. Calculate the horizontal force required to move the plate with a speed of 3 cm per second.
[Hint: `F=-etaA(dv)/(dx)."Here"(dv)/(dx)=(3xx10^(-2)ms^(-1))/(2xx10^(-3))=15s^(-1)`.]
