with a momentum that never lets up 
(ROOT (PP (IN with) (NP (NP (DT a) (NN momentum)) (SBAR (WHNP (WDT that)) (S (ADVP (RB never)) (VP (VBZ lets) (PRT (RP up))))))))
(ROOT (PP (IN ) (NP (NP (DT ) (NN )) (SBAR (WHNP (WDT )) (S (ADVP (RB )) (VP (VBZ ) (PRT (RP ))))))))