Using the kinematic equation d = V_0 * t + 1/2 * a * t^2, where d is height you can rewrite this to be d = 1/2*g*t^2 or 4.9t^2
g = a because this is a free fall
d = 1/2 * 9.81m/s^2 * 2.5^2
d = 30.65625m
d = 30.7m
Gravitational potential energy, relative to some level =
(mass of the object)
times
(height above the reference level)
times
(acceleration due to gravity) .
The volume of every sphere is
Volume = (4/3) (pi) (radius)³
When you say "across", I think you mean the diameter of the ball.
The radius is half of the diameter = 12 inches.
Volume = (4/3) (pi) (12 inches)³
= (4/3) (pi) (1,728 cubic inches)
= 7,238.2 cubic inches . (rounded)