The relative velocity of two consecutive layers is 8cm/s. If the perpendicular distance between the layers is 0.1 cm, then the velocity gradient will be

We know that,

Velocity gradient $=\frac{\mathrm{dv}}{\mathrm{dx}}$

where dx is the perpendicular distance between the layers and dv is the relative velocity of two successive layers.

Velocity gradient $=\frac{\mathrm{dv}}{\mathrm{dx}}=\frac{8}{0.1}=80{\mathrm{s}}^{-1}$

Hence the correct answer is 80.