A solid disk of mass and radius is rigidly fastened coaxially to a thin hoop of mass…

PHYSICS · Multi-part · AP · Physics C: Mechanics · Torque and Rotational Dynamics · Torque and Rotational Dynamics

Problem

A solid disk of mass

2.0\,\text{kg}

and radius

0.15\,\text{m}

is rigidly fastened coaxially to a thin hoop of mass

1.5\,\text{kg}

and radius

0.25\,\text{m}

to form a composite flywheel. The assembly spins as a single rigid object about their common central axis, which is perpendicular to their planes. (a) Calculate the rotational inertia of the composite flywheel about its central axis. (b) The flywheel is brought from rest to an angular speed of

600\,\text{rev}\,\text{min}^{-1}

by a motor that delivers constant power. Determine the minimum work that must be done on the flywheel during the spin-up. (c) If the motor delivers

2.0\,\text{kW}

of mechanical power, estimate the shortest possible time required to reach the final angular speed found in part (b).

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