We are to find how long will it take to return to the ground?
Answer:
t = 0.48 sec
Step-by-step explanation:
We are given;
initial velocity; vi = 40 ft/s
hi = 70 ft
acceleration due to gravity; a = 32 ft/s²
Now, we are given that the rocket's height as a function of time is;
h = -12at² + vit + hi
At ground, h = 0
Plugging in the relevant values to obtain ;
0 = -12(32)t² + 40t + 70
-384t² + 40t + 70 = 0
The roots of the equation gives; t = 0.48 sec
