( ( As ( ( the ( centripetal force ) ) ( acts ( upon ( ( an object ) ( moving ( in ( ( a circle ) ( at ( constant speed ) ) ) ) ) ) ) ) ) ) ( , ( ( the force ) ( always ( ( ( acts inward ) ( as ( ( ( the velocity ) ( of ( the object ) ) ) ( is ( ( directed tangent ) ( to ( the circle ) ) ) ) ) ) ) . ) ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (DT the) (JJ centripetal) (NN force)) (VP (VBZ acts) (PP (IN upon) (NP (NP (DT an) (NN object)) (VP (VBG moving) (PP (IN in) (NP (NP (DT a) (NN circle)) (PP (IN at) (NP (JJ constant) (NN speed))))))))))) (, ,) (NP (DT the) (NN force)) (ADVP (RB always)) (VP (VBZ acts) (ADJP (JJ inward)) (SBAR (IN as) (S (NP (NP (DT the) (NN velocity)) (PP (IN of) (NP (DT the) (NN object)))) (VP (VBZ is) (VP (VBN directed) (NP (NN tangent)) (PP (TO to) (NP (DT the) (NN circle)))))))) (. .)))
As the centripetal force acts upon an object moving in a circle at constant speed, the force always acts inward as the velocity of the object is directed tangent to the circle.
(ROOT (S (NP (JJ Centripetal) (NNS forces)) (VP (VBP cause) (S (NP (NNS objects)) (VP (TO to) (VP (VB turn) (PRT (RP around)) (ADVP (RB continuously)) (PP (IN in) (NP (DT a) (NN circle))))))) (. .)))