A solid cylinder of mass m and radius r starts rolling down an inclined plane of inclination `theta`. Friction is enough to prevent slipping. Find the speed of its centre of mass when its centre of mass has fallen a height `h`.

Explanation

To solve the problem, we will use the principle of conservation of energy. The total mechanical energy at the top of the incline will be equal to the total mechanical energy when the center of mass has fallen a height \( h \).

### Step-by-Step Solution:

1. **Identify Initial and Final States:**
- At the initial position (top of the incline), the cylinder is at rest, so its initial kinetic energy is \( 0 \).
- The potential energy at this position is given by \( PE_1 = mgh \), where \( h \) is the height fallen.
- At the final position (after falling height \( h \)), the cylinder has both translational and rotational kinetic energy.
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