( It ( ( is ( ( the sum ) ( of ( ( an ( object 's ) ) ( ( ( kinetic and ) potential ) energy ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (NP (NP (DT the) (NN sum)) (PP (IN of) (NP (NP (DT an) (NN object) (POS 's)) (ADJP (JJ kinetic) (CC and) (JJ potential)) (NN energy))))) (. .)))
It is the sum of an object's kinetic and potential energy.
(ROOT (S (NP (NP (DT The) (NN sum)) (PP (IN of) (NP (NP (DT the) (JJ kinetic) (CC and) (JJ potential) (NNS energies)) (PP (IN of) (NP (NP (DT a) (NN system) (POS 's)) (NNS atoms) (CC and) (NNS molecules)))))) (VP (VBZ is) (VP (VBN called) (NP (JJ internal) (NN energy)))) (. .)))