Question

A solid circular disk has a mass of 1.67 kg and a radius of 0.144 m. Each of three identical thin rods has a mass of 0.351 kg. The rods are attached perpendicularly to the plane of the disk at its outer edge to form a three-legged stool (see the figure). Find the moment of inertia of the stool with respect to an axis that is perpendicular to the plane of the disk at its center. (Hint: When considering the moment of inertia of each rod, note that all of the mass of each rod is located at the same perpendicular distance from the axis.)

Answer 1

3 m r^2 + (1/2) M r^2
where M = 1.67
and
m = .351
and
r = .144