# Liquid Friction!

**Classical Mechanics**Level 5

A Thin

Find the

**circular**disk of radius \(R\), rotates in a cylindrical chamber, which is filled with water (coefficient of viscosity \(\eta\)). It is rotated with**constant**angular velocity \(\omega\).Find the

**Power**developed (in**watts**)by the viscous forces, if the distance between the top-bottom walls and the disk is \(h\).**Details and Assumptions:**

\(\bullet\) Neglect end effects.

\(\bullet\) \(\eta = 8.9\times 10^{-4}\)

\(\bullet\) \(R = 2m\)

\(\bullet\) \(h = 1mm\)

\(\bullet\) \(w = 2 rad/s\)