Further Mechanics
What is contributing to the centripetal force at each point in the cycle. This is for a ball spun on a string:

A : the weight of the ball is directly contributing to the centripetal force since it is acting directly towards the center of a circle. Force on a string is minimal.
B: the weight of the ball is acting perpendicular to the direction of the centripetal force, the string provides the full force.
C: the weight of the ball is acting opposite to the direction of the centripetal force.