s=1/2(a1)tt+1/2(a2)TT
50=1/2*(a1)*12*12+1/2(a2)8*8 且初末速度都为0.∴(a1)t+(a2)t=0
解得:a1= a2=
然后v=a1*t=(a1)*12=?
结果自己算.有分数.