(1)mgh=μmgSS=0.8/0.2=4m(2)mgh=mVB^2/2F-mg=mVB^2/R联立F=42N(3)上一问中VB=√2gh=√2*10*0.8=4m/s在此之后用动正洞量守恒mVB=(m+M)V'V'=4/4=1m/s小车不固定时物块再次停皮清念在小车上时距燃困小车 B 点的距离为S'mgh-(m+M)V'^2/2=μmgS'S'=
①4m②42N③3m④4:3