( ( ( ( The impulse ) ( of ( the force ) ) ) ( is ( calculated ( by ( ( multiplying ( that force ) ) ( by ( ( the length ) ( of time ) ) ) ) ) ) ) ) ( it ( acts . ) ) )
(ROOT (S (S (NP (NP (DT The) (NN impulse)) (PP (IN of) (NP (DT the) (NN force)))) (VP (VBZ is) (VP (VBN calculated) (PP (IN by) (S (VP (VBG multiplying) (NP (DT that) (NN force)) (PP (IN by) (NP (NP (DT the) (NN length)) (PP (IN of) (NP (NN time))))))))))) (NP (PRP it)) (VP (VBZ acts)) (. .)))
The impulse of the force is calculated by multiplying that force by the length of time it acts.
(ROOT (S (NP (NNP Impulse)) (VP (VBZ is) (NP (NP (DT the) (NN quantity)) (PP (IN of) (NP (NP (NN force)) (VP (VBN multiplied) (PP (IN by) (NP (NP (DT the) (NN time)) (SBAR (S (NP (PRP it)) (VP (VBZ is) (VP (VBN applied)))))))))))) (. .)))