( ( ( the sum ) ( of ( the ( kinetic ( and ( potential energies ) ) ) ) ) ) ( of ( ( all particles ) ( in ( the system ) ) ) ) )
(ROOT (NP (NP (NP (DT the) (NN sum)) (PP (IN of) (NP (DT the) (JJ kinetic) (CC and) (JJ potential) (NNS energies)))) (PP (IN of) (NP (NP (DT all) (NNS particles)) (PP (IN in) (NP (DT the) (NN system)))))))
the sum of the kinetic and potential energies of all particles in the system
(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)))) (. .)))