Physics

Problem

A flywheel initially at rest has rotational inertia

0.20\,\text{kg}\,\!\cdot\!\text{m}^2

. A motor supplies a constant

1.2\,\text{N}\,\!\cdot\!\text{m}

torque. Exactly

4.0\,\text{s}

after the motor starts, a mechanism retracts two masses so the rotational inertia instantly decreases to

0.12\,\text{kg}\,\!\cdot\!\text{m}^2

. The motor torque remains unchanged. Determine the angular speed of the flywheel

6.0\,\text{s}

after the motor first starts.