A cylinder of mass M, radius `r_(1)` and lenglth l is kept inside another cylinder of radius `r_(2)` and length l. The space between them is filled with a liquid of viscosity `eta`. The inner cylinder starts rotating with angular velocity `omega` while the other cylinder is at rest. Find time when inner cylinder stops.

Explanation

To solve the problem, we will follow these steps:

### Step 1: Understand the System
We have two concentric cylinders: an inner cylinder of radius \( r_1 \) and an outer cylinder of radius \( r_2 \). The space between them is filled with a viscous liquid of viscosity \( \eta \). The inner cylinder starts rotating with an angular velocity \( \omega \), while the outer cylinder remains at rest.

### Step 2: Determine the Viscous Force
The viscous force \( F \) acting on the inner cylinder can be expressed using the formula:
\[
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