physics
posted by Johnathan .
A 0.21 kg ball on a string is whirled on a vertical circle at a constant speed. When the ball is at the three o'clock position, the tension is 18 N.

(a) How does the magnitude of the centripetal force acting on the ball relate to each point on the circle? The magnitude is the same at each point on the circle.
The magnitude is not the same at each point on the circle.
There is insufficient information for a definitive answer.
Is the answer the magnitude is not the same at each point on the circle?

No. The magnitiude is the same. Only the direction of the force changes.