When a free body diagram of a ball being swung in a circle is drawn (example), only tension and weight are drawn on it. I understand that the centripetal force equals tension plus weight at the top of the circle, and tension minus weight at the bottom of it, but there must also always be an equal centrifugal force because of Newton's 3rd Law. Since this force also comes into play, why isn't it drawn on the free body diagram? To me, the diagram seems incomplete without showing it, yet I don't recall ever seeing centrifugal force shown on this type of free body diagram.
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