Question

a player throws a ball vertically upward the ball attains a height of 25m and then returns back calculate the initial speed

Answer 1

Velocity at the highest point is zero.
Because at this point the kinetic energy of the body is zero. The body comes under the total influence of gravitational potential at this point.

And direction of acceleration is negative that of velocity as the velocity is decreasing as the body is going upward.
So as the man threw the ball upward, direction of acceleration is downward.

Thanks.
Tripathy