=PIR(L-x)8-PIR'Z prR gr d2x,2 x=0 记 2a2 g →"+m2x=0 d t 2丌 →x=C1C0SOr+C2SinO兮O T PgR 今m =19525(kg) =10 m38=9.:8m/,R=0,25mx=314 S= R l − x g − R l  g 2 2  ( )  R gx 2 = − 0 2 2 2  + x = m R g dt d x  记 m R g 2 2   = 0 2 2 2  + x = dt d x  x c cost c sint  = 1 + 2     = = T 2 195.25( ) 2 kg gR  m = =   3 3 10 m kg  = 8 2 9. s g = m R = 0.25m  = 3.14