there are two equations v=u+at and s=ut+(1/2)atē

from the first question ,if we set the time to v=0 to find time(t)(which is half of the flying time),

we get

0=u-(g/2)t

(g/2)t=u

t=2u/g ----- (1) to find the total,we have to multiply by 2. so t=4u/g

when the displacement is 0,we can find the total flying time using:

s=ut+(1/2)atē

0=ut-(g/2)tē

t{u-(g/2)t}=0

(g/2)t=u or t=0

t=2u/g ,not 4u/g

aren't both equations suppose to give the same answer?