( Work ( ( is ( defined ( as ( force ( acting ( on ( ( an object ) ( in ( ( the direction ) ( of motion ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Work)) (VP (VBZ is) (VP (VBN defined) (PP (IN as) (NP (NP (NN force)) (VP (VBG acting) (PP (IN on) (NP (NP (DT an) (NN object)) (PP (IN in) (NP (NP (DT the) (NN direction)) (PP (IN of) (NP (NN motion)))))))))))) (. .)))
Work is defined as force acting on an object in the direction of motion.
(ROOT (S (NP (NNP Work)) (VP (VBZ is) (VP (VBN done) (SBAR (RB only) (IN if) (S (NP (DT a) (NN force)) (VP (VBZ is) (VP (VBN exerted) (PP (IN in) (NP (NP (DT the) (NN direction)) (PP (IN of) (NP (NN motion))))))))))) (. .)))