( ( Force ( in ( the equation ) ) ) ( ( can ( be ( thought ( of ( as ( ( the thrust ) ( of ( the ( rocket engine ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Force)) (PP (IN in) (NP (DT the) (NN equation)))) (VP (MD can) (VP (VB be) (VP (VBN thought) (PP (IN of) (IN as) (NP (NP (DT the) (NN thrust)) (PP (IN of) (NP (DT the) (NN rocket) (NN engine)))))))) (. .)))
Force in the equation can be thought of as the thrust of the rocket engine.
(ROOT (S (NP (NNP Thrust)) (VP (VBZ is) (NP (NP (DT the) (NN force)) (VP (VBG pushing) (NP (DT a) (NN rocket))))) (. .)))