A uniform spherical shell of mass 8.90 {\rm kg} with diameter46.0 {\rm cm} has four small masses of 0mass 2.40 {\rm kg} attached to its outer surface and equally spaced around it. This combination is spinning regarding an axis running during the center of the sphere and two of the small masses.
a. What friction torque is required to reduce its angular speed from76.0 {\rm rpm} to 46.0 {\rm rpm} in a time interval of30.0 {\rm s}?