A 合力F=mgsinα=ma推出a=gsinα=6m/s t=v/a=1s设B竖直位移h，水平位移s1h=1/2gt^2 s=v0t tanα=h/s1=gt/2v0 t=1s v0=5m/s2as=v^2 s=3mh1=s*sinα=3*0.6=1.8mh2=1/2gt^2=5mh=6.8m
