1)K=F/Δx=1N÷(0.11m-0.1m)=100N/m2)f滑=μG=400N×0.25=100N推力70N时,受静摩擦力f1=F1=70N推力150N时,受滑动摩擦力f2=f滑=100N3.1)0.5a1t1�0�5=S0.5a1×(5s)�0�5=2.5ma1=0.2m/s�0�5F-f1=ma13N-f1=12Kg×0.2m/s�0�5f1=0.6N3.2)V=a1t1=0.2m/s�0�5×5s=1m/sa2=V�0�5/(2S2)=(1m/s)�0�5/(2×5m)=0.1m/s�0�5f1+f2-F=ma20.6N+f2-3N=12Kg×0.1m/s�0�5f2=3.6N
1、100N/S;2、70N、100N;一、0.6N;二、4.5N