A ball at the end of a string is being swung in a vertical circle at a constant velocity. Which of these statements about the forces acting on the ball and the acceleration of the ball are true?
a. The tension in the string at the top of its circular path and the bottom of its circular path are equal in magnitude.
b. At the bottom of the circular path, the tension in the string acts up while the acceleration of the ball is down.
c. The string is perfectly horizontal two times in the circular path, once on the way up and once on the way down. The only difference in the net force between these situations is the direction of the tension force.
d. At the top of its circular path, the tension in the string acts down while the acceleration of the ball is up