Answer:
The ball hit the ground at t=6 seconds
Explanation:
we have

where
f(t) is he height of the ball in feet
t is the time in seconds
we know that
When the ball hit the ground, the height of the ball is equal to zero
so
For f(t)=0

solve for t
Factor the leading coefficient -16t

the solutions are
t=0, t=6
Remember that
For t=0 ----> f(t)=0 is the initial height of the ball
Fort=6 sec ----> f(t)=0
therefore
The ball hit the ground at t=6 seconds