3 dU=13tdt→7 0 0 dx 3 3 t2→dx=-t2dt dt 2 2 3 ∵W=16t.-t2dt t4=36J 2 0 常见错误之一 F 3t s=vnt+1at2=1.3t.t2=153=1.5×23=12m W=F·s=6×2×12=144J6 2 12 144J 3 1.5 1.5 2 12m 2 1 2 1 3 2 2 3 3 0 =  =   = = + =   = =  = = = W F s s t at t t t t m F a v 常见错误之一： 36J 4 9 d 2 3 6 d 2 3 d 2 3 d d 2 3 d 3 d 2 0 4 2 0 2 2 2 0 0 2  =       =  = =  = =  =    W t t t t t x t t t x t t t v t v v