The supporting force of the ground to hands: f = g× oaob = 600 n×1m1.5m = 400 n;
(2)W = nFS = 30×400n×0.5m = 6000j；
(4)P=Wt=6000J60s= 100W。
Answer: (1) The ground opponent's supporting force is 400 N;
(2) The work done by Xiao Ming at 1 min is 6000 J;
(3) Xiaoming's working power is100 W.