A Bead with a mass 10g can slide without friction on a circular motion massless hoop that is in a vertical plane and has a radius of 5 cm. The hoop rotates at a constant rate of 4rev/s about a vertical diameter.Find
a) the distance from the bead to the axis of rotation in vertical equilibrium;
b) the magnitude and direction of the bead's acceleration;
c) what work should be done by friction in order to stop the hoop.