$2-94$ A thin plate moves between two parallel, horizontal stationary that surfaces at a constant velocity of $5\frac{m}{s}.$ The two stationary surfaces are spaced $4$ cm apar, and the medium between them is filled with oil whase viscosity is $0\mathrm{.}9N*s^2{m}^2$ The part of the plate immersed in oil at any given time is $2-$m long and $0\mathrm{.}5-m$ wide. If the plate moves through the mid$-$plane between the surfaces. determine the force required to maintain this motion. What would your response be if the plate was $1$ cm from the bottom surface $(h_2)$ and $3$ cm from the top surface $(h_1)?$

FIGURE P$2-94$

$2-95$ Reconsider Prob. $2-94.$ If the viscosity of the oil above the moving plate is $4$ umes that of the oil helow the plate, determine the distance of the plate from the bottom surface $\{\begin{array}{c}{h}_2\end{array}\}$ that will minimize the force needed to pull the plate between the two oils at constant velocity