A 1.3-kg 10-cm-diameter solid sphere is rotating about its diameter at 77 rev/min.

Question

(a) What is its kinetic energy?

(b) If an additional 5.0 mJ of energy are supplied to the rotational energy, what is the new angular speed of the ball?
rev/min

Answer 1

a) if it is rolling , it has rotational ke 1/2 I w^2, and translational KE 1/2 m v^2

To relate these, consider w*r=v

KE= 1/2 I v^2/r^2 + 1/2 m v^2

but I for a solid sphere is... 2/5 mr^2, so put that in for I, and compute.