Answer:
a) Initial speed of the ball = 14.45 m/s
b) At height 6 m speed of ball = 9.55 m/s
c) Maximum height reached = 10.65 m
Explanation:
a) We have equation of motion
, where s is the displacement, u is the initial velocity, t is the time taken and a is the acceleration.
s = 6 m, t = 0.5 seconds, a = acceleration due to gravity value = -9.8
Substituting

Initial speed of the ball = 14.45 m/s
b) We have equation of motion
, where v is the final velocity
s = 6 m, u = 14.45 m/s, a = -9.8
Substituting

So at height 6 m speed of ball = 9.55 m/s
c) We have equation of motion
, where v is the final velocity
u = 14.45 m/s, v =0 , a = -9.8
Substituting

Maximum height reached = 10.65 m