( ( ( ( inelastic ( collision ( COLLIDE ELASTIC ) ) ) , ) NOT ) . )
(ROOT (NP (NP (JJ inelastic) (NN collision) (NNP COLLIDE) (NNP ELASTIC)) (, ,) (NP (NNP NOT)) (. .)))
inelastic collision COLLIDE ELASTIC, NOT.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NN gas) (NNS particles)) (VP (VBP collide)))) (, ,) (NP (DT these) (NNS collisions)) (VP (VBP are) (VP (VBN considered) (S (ADJP (JJ elastic))))) (. .)))