( ( One approach ) ( ( is ( to ( ( attach ( ( simple machines ) ( in series ) ) ) ( to ( obtain ( compound machines ) ) ) ) ) ) . ) )
(ROOT (S (NP (CD One) (NN approach)) (VP (VBZ is) (S (VP (TO to) (VP (VB attach) (NP (NP (JJ simple) (NNS machines)) (PP (IN in) (NP (NN series)))) (S (VP (TO to) (VP (VB obtain) (NP (JJ compound) (NNS machines))))))))) (. .)))
One approach is to attach simple machines in series to obtain compound machines.
(ROOT (S (NP (NNS Scissors)) (VP (VBP are) (NP (JJ compound) (NNS machines))) (. .)))