Explanation:
The equation of motion of an object is given by :
[tex]h(t)=-16t^2+112t+128[/tex]
Where
t is the time in seconds
We need to find the time when the object hits the ground. When the object hits the ground, h(t) = 0
So,
[tex]-16t^2+112t+128=0[/tex]
[tex]-t^2+7t+8=0[/tex]
On solving above equation using online calculator, t = 8 seconds. So, the object hit the ground after 8 seconds. Hence, this is the required solution.