Question

if i had a ball on a sting, and i started to swing the ball above my head, the forces would act like this :
i wants to keep the ball going in a straight line
in the string keeps it from going straight (pull from linear path)
is equal and opposite to above force in the string (pull on string)

Explanation:

1. The first blank: In circular motion, inertia (Newton's first law) makes an object tend to move in a straight line. So "Inertia" wants to keep the ball going in a straight line.
2. The second blank: The tension in the string provides the centripetal force that pulls the ball towards the center, keeping it from moving straight. So "Tension" in the string keeps it from going straight.
3. The third blank: By Newton's third law, the ball exerts an equal and opposite force (centrifugal - like reaction force, but in terms of action - reaction, it's the ball's pull on the string) on the string. So "The ball's pull" (or "Reaction force" related to the tension) is equal and opposite to the tension force in the string.

Answer:

1. Inertia
2. Tension
3. The ball's pull (or Reaction force)