Here, ball is released... and it is in free fall means with zero initial velocity.
We know, s = ut + 1/2 at²
Here, s = 1000 m
u = 0
a = 10 m/s2
Substitute their values,
1000 = 0 + 1/2 * 10 * t²
2000 = 10 * t²
t² = 2000 /10
t = √200
t = 14.14 s
In short, Your Answer would be 14.14 seconds
Hope this helps!