A viscous liquid is sheared between two parallel disks of radius \(R\), one of which rotates while the other is fixed. The velocity field is purely tangential, and the velocity varies linearly with \(z\) from \(V_{\theta}=0\) at \(z=0\) (the fixed disk) to the velocity of the rotating disk at its surface \((z=h)\). Derive an expression for the velocity field between the disks.