Question 971729
s= 1/2 at^2   a=9.8 m/sec  units of s will be meters.

2s=at^2
t= sqrt ((2s/a)

t=8.08 sec.

vf=g*t
=9.8 m/sec^2 * 8 sec. 
78.4 m/sec.

Note:  if you set mgh=(1/2) mv^2, kinetic and potential energy, you get v= sqrt (2gh).  This way gives 79.2 m/sec.