A metal plate of the area 500   cm 2 is kept on a horizontal surface with a layer of oil of thickness 0 . 5   mm between them. The horizontal force required to drag the plate with a velocity of 2   cm   s - 1 is (coefficient of viscosity = 0 . 9   kg   m - 1   s - 1 )

Step-by-step solution

Here, we have to find out the horizontal force required to drag the plate kept on the metal surface since the fluid is viscous. Hence, the required force should be the viscous force, F = η A d V d x where η is coefficient of viscosity, A is the cross-section area and d V d x is the rate of shear deformation. ⇒ F = 0 . 9 × 500 × 10 - 4 × 2 × 10 - 2 0 . 5 × 10 - 3 ⇒ F = 0 . 9 × 2 = 1 . 8   N