Answer:
t = 54 seconds
Step-by-step explanation:
The equation that models the path of a rocket into the air is given by :
[tex]h(t)= -16t^2+864t[/tex]
It is required to find the time after which the rocket will hit the ground. When it hits the ground, the height of the rocket will becomes zero. It means,
h(t) = 0
i.e.
[tex]-16t^2+864t=0\\\\16t(-t+54)=0\\\\16t=0, -t+54=0\\\\t=0\ and\ t=54\ s[/tex]
It means after 54 seconds, the rocket will hit the ground.