Hellow!
For this use the next formula:
Vf = Vo + gt
Initial velocity is zero, so the formula simplificate:
Vf = gt
Data:
Vf = Final velocity = ?
g = Gravity = 9.8 m/s²
t = Time = 12 s
Replacing according our data:
Vf = 9.8 m/s² * 12 s
Vf = 117.8 m/s
The final velocity will be 117.8 meters per second.
