( Observers ( ( were ( required ( -LRB- ( i ( -RRB- ( to ( ( determine ( ( the direction ) ( of ( ( motion and ) ( -LRB- ( ii -RRB- ) ) ) ) ) ) ( to ( ( ( estimate and ) compare ) ( ( the ( ( velocities and ) distances ) ) ( travelled ( from ( distinct elements ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Observers)) (VP (VBD were) (VP (VBN required) (S (-LRB- -LRB-) (NP (FW i)) (-RRB- -RRB-) (VP (TO to) (VP (VB determine) (NP (NP (DT the) (NN direction)) (PP (IN of) (NP (NP (NN motion)) (CC and) (NP (-LRB- -LRB-) (NN ii) (-RRB- -RRB-))))) (S (VP (TO to) (VP (VB estimate) (CC and) (VB compare) (NP (NP (DT the) (NNS velocities) (CC and) (NNS distances)) (VP (VBN travelled) (PP (IN from) (NP (JJ distinct) (NNS elements))))))))))))) (. .)))
Observers were required (i) to determine the direction of motion and (ii) to estimate and compare the velocities and distances travelled from distinct elements.
(ROOT (S (NP (NP (NNP Distance)) (PP (IN over) (NP (NP (NN time)) (PP (IN in) (NP (DT a) (VBN given) (NN direction)))))) (VP (VBZ determines) (NP (NN velocity))) (. .)))