A thin hoop of unknown radius is mounted so that it can rotate freely about a…
PHYSICS · Multi-part · CBSE · Physics · System of Particles and Rotational Motion · System of Particles and Rotational Motion
Problem
A thin hoop of unknown radius is mounted so that it can rotate freely about a vertical axle through its center. An electric motor delivers 15J of rotational kinetic energy to the hoop during a very short time interval, after which the hoop is observed to be spinning at ω=6.0rads−1. Air resistance is negligible during the interval considered.
(a) Compute the rotational inertia of the hoop about the axle.
(b) The hoop is taken off its axle and its mass is measured to be 0.80kg. Determine the radius of the hoop.
(c) Describe how the answers to parts (a) and (b) would change, if at all, if the same amount of energy had been delivered over a longer time interval by a weaker motor. Provide a clear explanation rather than a calculation.