Answer:
a) Vf = 13.87[m/s]
b) t = 1 [s]
Step-by-step explanation:
a)
To solve this problem we can use kinematics equations:

where:
Vf = final velocity [m/s]
Vi = initial velocity = 4 [m/s]
h = elevation = 9 [m]
g = gravity acceleration = 9.81 [m/s^2]
![v_(f)=\sqrt{(4)^(2) +(2*9.81*9)}\\v_(f)=13.87[m/s]](https://img.qammunity.org/2021/formulas/physics/high-school/ih0waxe2dqi5f467sx3yotxlbyapzw0dw3.png)
b)
Now using the next equation we can find the time
![v_(f)=v_(i) +(g*t) \\t = (13.87-4)/9.81\\t=1[s]](https://img.qammunity.org/2021/formulas/physics/high-school/nuxhchp3jo4isl0ndtblypnapg09tmqafh.png)