( ( ( Slide ( the ( friction spider ) ) ) ( into ( the pulley ) ) ) . )
(ROOT (S (VP (VB Slide) (NP (DT the) (NN friction) (NN spider)) (PP (IN into) (NP (DT the) (NN pulley)))) (. .)))
Slide the friction spider into the pulley.
(ROOT (S (NP (VBG Sliding) (NN friction)) (VP (VBZ is) (NP (NP (NN friction)) (SBAR (WHNP (WDT that)) (S (VP (VBZ acts) (PP (IN on) (NP (NP (NNS objects)) (SBAR (WHADVP (WRB when)) (S (NP (PRP they)) (VP (VBP are) (VP (VBG sliding) (PP (IN over) (NP (DT a) (NN surface)))))))))))))) (. .)))