What is the velocity of the ball as it passes
The point A on its way up, where OA is one
Third the maximum heigh. The max height is 5 m. the accel is 10 m/s

Use

v^2= u^2 +2as

{where v is the final velocity,
u the initial velocity,
a the acceleration due to gravity,
s the displacement of the ball.}

To find the initial velocity that the ball is thrown. Put the values v=0, u=? a=10 and s=5.

Now you know u, use the same formula again to find the velocity when the displacement is a third of 5 m.