Question

A metal plate 5cm×5cm rest on a layer of castor oil 1mm thick whose coefficient of viscosity is 1.55Nsm^(-2). Find the horizontal force required to move the plate with a speed of 2 cms^(-1).

(a) 0.775N

(b) 0.0577N

(c) 0.0775N

(d) 0.577N

Answer 1

The correct answer is (c) 0.0775N

For explanation: F=ȠA dv/dx

F=1.55×25×10^-4×(2×10^-2)/(1×10^-3)=0.0775N.