Why does the theory of a body in circular motion leave us with unanswered questions? what are they?

Answer 1

What's gravity?

Answer 2

The only issue I know of is what's the nature of centripetal and centrifugal force? Many claim centrifugal force is not a force at all; they say centripetal force is the only true force. And that's the force that keeps the body going in a circle rather than flying out in a straight line according the Newton's first law.

Centripetal force stems from the string tugging on the ball in the ball/string system and from the force of gravity pulling on the moon in the moon/Earth system. But what is the source of centrifugal force?

The answer is that it's the change in velocity along the radius of the circle that is the source. But, wait, it's centripetal force that causes that change in velocity. So in a real sense, centrifugal force is simply a reaction to centripetal force. Thus, centripetal force is the only true force, centrifugal is just the reaction to it.

So the argument goes on...and it still is. Is centrifugal a true force or just a reaction to centripetal force? So that's the only unanswered question I know of.

Answer 3

What unanswered questions? If you understand the theory its fairly clear (it is to me, anyway).