Question

A solid cylinder of mass 20 kg rotates about its axis angular speed 100 rad s^-1. The radius of the cylinder is 0.25 m. What is the kinetic energy associated with the rotation of the cylinder? What is the magnitude of angular momentum of the cylinder about its axis?

Answer 1

(i) (K.E.)_rot = 1/2 Iω²

Here, I = 1/2 MR² = 20/2 x (0.25)² = 0.625 kg m²

ω = 100 rad s^-1

We get (K.E.)_rot = 1/2 x 0.625 x (100)² = 3125 J

Angular momentum,

L = Iω = (0.625) x 100 = 62.5 kg m² s^-1.