( Momentum ( ( refers ( to ( ( ( moving things ) , ) ( that ( ( is , ) ( ( the mass ) ( of ( ( an object ) ( multiplied ( by ( its velocity ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Momentum)) (VP (VBZ refers) (PP (TO to) (NP (NP (VBG moving) (NNS things)) (, ,) (SBAR (WHNP (WDT that)) (S (VP (VP (VBZ is)) (, ,) (NP (NP (DT the) (NN mass)) (PP (IN of) (NP (NP (DT an) (NN object)) (VP (VBN multiplied) (PP (IN by) (NP (PRP$ its) (NN velocity))))))))))))) (. .)))
Momentum refers to moving things, that is, the mass of an object multiplied by its velocity.
(ROOT (S (NP (NNP Momentum)) (VP (MD can) (VP (VB be) (VP (VBN calculated) (PP (IN by) (S (VP (VBG multiplying) (NP (NP (NP (DT an) (NN object) (POS 's)) (NN mass)) (PP (IN in) (NP (NP (NNS kilograms)) (PRN (-LRB- -LRB-) (NP (NN kg)) (-RRB- -RRB-))))) (PP (IN by) (NP (NP (PRP$ its) (NN velocity)) (PP (IN in) (NP (NP (NNS meters)) (PP (IN per) (NP (NP (JJ second)) (PRN (-LRB- -LRB-) (NP (NN m/s)) (-RRB- -RRB-)))))))))))))) (. .)))