Maximum height of a projectile

[Bugsy23]

I need to calculate the maximum height above sea level of a projectile. I already have the values for the initial velocity, the angle and the time of flight, and I have the following equation to calculate the y-component of the displacement from the launch point:
sy=uyt-1/2gt²
But how do I know at what time the projectile has reached its maximum height and begins accelerating downwards?

 

[sjb-2812]

I need to calculate the maximum height above sea level of a projectile. I already have the values for the initial velocity, the angle and the time of flight, and I have the following equation to calculate the y-component of the displacement from the launch point:
sy=uyt-1/2gt²
But how do I know at what time the projectile has reached its maximum height and begins accelerating downwards?

Do you know any equations that relate initial velocity, acceleration, time and final velocity?

 

[Naty1]

Note the vertical velocity is zero at the maximum height...

 

[Sakriya]

calculated it... H=(u^2 sin2A)/g

 

[willem2]

calculated it... H=(u^2 sin2A)/g

Assuming you meant $sin^2 A$ and not sin(2A) it's correct, except
for a factor (1/2) that you're missing.