Question

A drum major twirls a 96-cm-long, 400 g baton about its center of mass at 100 rpm. What is the baton’s rotational kinetic energy?

Answer 1

moment of inertia of baton about its center of mass,
I = M L^2 / 12

I = (0.400 kg)(0.96m)^2 / 12 = 0.03072 kg m^2

and w = 100 rpm = 100 x 2pi rad / 60 s

w = 10.47 rad/s

rotational KE = I w^2 / 2

= (0.03072 kg m^2)(10.47 rad/s)^2 / 2

= 1.68 J ..........Ans