h =1/2gt, t=√2h/g=√2×5/10=1s, V ⊥=gt =10×1=10m/s, V 合=√Vo+V ⊥=√10+10=14.14m*s tgα=V ⊥/vo=1, α=45°麻烦采纳，谢谢!
