( You ( ( ( should only ) ( rotate ( on ( ( one axis ) ( at ( a time ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP You)) (VP (MD should) (ADVP (RB only)) (VP (VB rotate) (PP (IN on) (NP (NP (CD one) (NNS axis)) (PP (IN at) (NP (DT a) (NN time))))))) (. .)))
You should only rotate on one axis at a time.
(ROOT (S (NP (PRP It)) (VP (VBZ takes) (NP (NN earth) (CD one) (NN week)) (S (VP (TO to) (VP (VB rotate) (PP (IN on) (NP (PRP$ its) (NNS axis))) (NP (CD seven) (NNS times)))))) (. .)))