height = 20 ft
equation
h(t) = -16t^2 + 20
time to hit the ground
Substitution
20 = -16t^2 + 20
-20 = -16t^2 + 20
-20 - 20 = -16t^2
-40 = -16t^2
-40/-16 = t^2
t^2 = 40/16
t^2 = 5/2
t = 1.58 s
b) Using the equation given and considering that the height will be negative.
