In the figure $($example problem from Chapter $4),$ consider a non$-$steady state process or flow between two parallel plates $($water at room temperature$).$ The velocity in x direction is both a function of distance, $y$ and time $t.$ Navier$-$Stokes equation for the velocity will be:

$\frac{\text{d}\text{e}\text{l}\text{u}}{\text{d}\text{e}\text{l}\text{t}}=\frac{de{l}^{2}u}{del{y}^2}$

Where, $$ is density of water and $$ is viscosity of water. The upper plate is suddenly put on a motion with velocity $V=2\mathrm{.}5\frac{m}{s}.$ The distance between two plates is