( ( ( ( Gravitational ( potential energy ) ) ( -LRB- ( PE -RRB- ) ) ) ( -LRB- ( ( work ( done ( by ( the ( gravitational force ) ) ) ) ) -RRB- ) ) ) ( ( is ( ( ( ( ( converted ( into ( ( kinetic energy ) ( -LRB- ( KE -RRB- ) ) ) ) ) , ) and ) then ) ( ( ( ( ( randomized ( by ( ( viscosity and ) turbulence ) ) ) ( into ( ( increased ( average ( kinetic energy ) ) ) ( of ( ( atoms and ) molecules ) ) ) ) ) ( in ( the system ) ) ) , ) ( producing ( a ( temperature increase ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NP (JJ Gravitational) (JJ potential) (NN energy)) (PRN (-LRB- -LRB-) (NP (NNP PE)) (-RRB- -RRB-))) (PRN (-LRB- -LRB-) (NP (NP (NN work)) (VP (VBN done) (PP (IN by) (NP (DT the) (JJ gravitational) (NN force))))) (-RRB- -RRB-))) (VP (VBZ is) (VP (VP (VBN converted) (PP (IN into) (NP (NP (JJ kinetic) (NN energy)) (PRN (-LRB- -LRB-) (NP (NNP KE)) (-RRB- -RRB-))))) (, ,) (CC and) (ADVP (RB then)) (VP (VBN randomized) (PP (IN by) (NP (NN viscosity) (CC and) (NN turbulence))) (PP (IN into) (NP (NP (VBN increased) (JJ average) (NN kinetic) (NN energy)) (PP (IN of) (NP (NNS atoms) (CC and) (NNS molecules))))) (PP (IN in) (NP (DT the) (NN system))) (, ,) (S (VP (VBG producing) (NP (DT a) (NN temperature) (NN increase))))))) (. .)))
Gravitational potential energy (PE) (work done by the gravitational force) is converted into kinetic energy (KE), and then randomized by viscosity and turbulence into increased average kinetic energy of atoms and molecules in the system, producing a temperature increase.
(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)))) (. .)))