( ( 2 -RRB- ) ( ( State ( ( the friction ) ( ( force ( on ( a object ) ) ) ( before it ) ) ) ) ( slides . ) ) )
(ROOT (S (LST (LS 2) (-RRB- -RRB-)) (NP (NP (NNP State)) (SBAR (S (NP (DT the) (NN friction)) (VP (VBP force) (PP (IN on) (NP (DT a) (NN object))) (PP (IN before) (NP (PRP it))))))) (VP (VBZ slides)) (. .)))
2) State the friction force on a object before it slides.
(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)))))))))))))) (. .)))