Parabolic Motion, equation for t

[RobSchneider]

I'd like to know why

t= v - u/a

will not get me a correct value for t when v= final velocity, u= initial velocity and a=acceleration, when the final velocity of the projectile along the y axis=0.

 

[haruspex]

I hope you mean t= (v - u)/a.
Please show your working so that we can see where you go wrong. Are you perhaps forgetting to make a negative?

 

[mfb]

What do you mean with "parabolic motion"?
Maybe the acceleration is not constant?