( Forces ( ( can ( be ( ( ( represented ( by vectors ) ) , ) ( since ( they ( have ( ( both ( a ( ( size and ) direction ) ) ) ( of action ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Forces)) (VP (MD can) (VP (VB be) (VP (VBN represented) (PP (IN by) (NP (NNS vectors))) (, ,) (SBAR (IN since) (S (NP (PRP they)) (VP (VBP have) (NP (NP (CC both) (DT a) (NN size) (CC and) (NN direction)) (PP (IN of) (NP (NN action)))))))))) (. .)))
Forces can be represented by vectors, since they have both a size and direction of action.
(ROOT (S (NP (NNP Vector)) (VP (VBZ is) (NP (NP (DT a) (NN measure)) (SBAR (WHNP (WDT that)) (S (VP (VBZ has) (NP (DT both) (NN size) (CC and) (NN direction))))))) (. .)))