( ( ( ( ( ( From ( ( ( Newton 's ) ( first law ) ) ( of motion ) ) ) ( we ( know ( that ( ( ( an object ) ( at rest ) ) ( will ( stay ( at rest ) ) ) ) ) ) ) ) , ) and ) ( ( ( an object ) ( in ( motion ( -LRB- ( ( constant velocity ) -RRB- ) ) ) ) ) ( will ( ( stay ( in motion ) ) ( unless ( ( acted on ) ( by ( an ( external force ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (PP (IN From) (NP (NP (NP (NNP Newton) (POS 's)) (JJ first) (NN law)) (PP (IN of) (NP (NN motion))))) (NP (PRP we)) (VP (VBP know) (SBAR (IN that) (S (NP (NP (DT an) (NN object)) (PP (IN at) (NP (NN rest)))) (VP (MD will) (VP (VB stay) (PP (IN at) (NP (NN rest))))))))) (, ,) (CC and) (S (NP (NP (DT an) (NN object)) (PP (IN in) (NP (NP (NN motion)) (PRN (-LRB- -LRB-) (NP (JJ constant) (NN velocity)) (-RRB- -RRB-))))) (VP (MD will) (VP (VB stay) (PP (IN in) (NP (NN motion))) (SBAR (IN unless) (S (VP (VBD acted) (PRT (RP on)) (PP (IN by) (NP (DT an) (JJ external) (NN force))))))))) (. .)))
From Newton's first law of motion we know that an object at rest will stay at rest, and an object in motion (constant velocity) will stay in motion unless acted on by an external force.
(ROOT (S (SBAR (IN If) (S (NP (DT no) (JJ unbalanced) (NN force)) (VP (VBZ acts) (PP (IN on) (NP (DT an) (NN object)))))) (NP (DT the) (NN object)) (VP (VBZ remains) (PP (PP (IN at) (NP (JJ constant) (NN velocity))) (CC or) (PP (IN at) (NP (NN rest))))) (. .)))