A rigid object of mass 2.0kg and radius 0.30m spins about its central axis with an angular speed of 10rad/s. Its rotational kinetic energy is measured to be 9J. Which of the following objects could it be? (All objects have the same mass and radius.)
a) A solid cylinder
b) A thin spherical shell (hollow sphere)
c) A thin hoop
d) A thin rod of length 0.60m hinged at its center