Question

In the previous question, the net force exerted by fluid on moving plate is

Answer 1

$F = \eta A \frac{v}{d}$

Answer 2

A thin fluid layer between a moving plate and a stationary surface results in a shear stress $\tau = \eta \frac{v}{d}$. Multiplying by the area A gives the net force $F = \eta A \frac{v}{d}$.