( Weight ( ( is ( ( caused ( by ( ( the force ) ( of gravity ) ) ) ) ( acting ( on ( a body ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Weight)) (VP (VBZ is) (VP (VBN caused) (PP (IN by) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NN gravity))))) (S (VP (VBG acting) (PP (IN on) (NP (DT a) (NN body))))))) (. .)))
Weight is caused by the force of gravity acting on a body.
(ROOT (S (NP (NNP Gravity)) (VP (VBZ causes) (S (NP (NNS rocks)) (VP (TO to) (VP (VB roll) (ADVP (RB downhill)))))) (. .)))