( ( Calculate ( elastic ( potential energy ) ) ) . )
(ROOT (S (VP (VB Calculate) (NP (JJ elastic) (JJ potential) (NN energy))) (. .)))
Calculate elastic potential energy.
(ROOT (S (S (VP (VBG Changing) (NP (NP (DT the) (NN shape)) (PP (IN of) (NP (DT an) (JJ elastic) (NN material)))))) (VP (VBZ gives) (NP (PRP it)) (NP (JJ potential) (NN energy))) (. .)))