Answer:
7 seconds
Step-by-step explanation:
You gave the height formula at any time t as
h = -16t^2 + 112t
when the object hits the ground, that means that h = 0. Putting this value in the equation above, we get
-16t^2 + 112t = 0 --> -16t + 112 =0
Solving for t, we get
t = 112/16 = 7 seconds