Question

Figure $11-45$ shows a rigid structure consisting of a circular hoop of radius $R$ and mass $m$ and a square made of four thin bars, each of length $R$ and mass $m$. The rigid structure rotates at a constant speed about a vertical axis, with a period of rotation of $2.5s$. Assuming $R=0.50m$ and $m=2.0kg$, calculate its angular momentum about that axis.

Answer 1

The angular speed is constant:
$\omega =\frac{\Delta \theta }{\Delta t}=\frac{2\pi }{25}=2.5rad/s$.
Thus $L=I_{total}=4.0kg.m^2/s$.