
Arturo O. answered 10/25/16
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The height of the football as a function of time obeys the equation:
h(t) = (1/2)at2 + v0t + h0
where
t = time since kick, in seconds
a = -g = -32 ft/s2
v0 = 32 ft/s
h0 = 0 if kicked from the ground
Then
h(t) = -16t2 + 32t
The ball hits the ground when h(t) = 0:
0 = -16t2 + 32t
Just solve for t. You will get two solutions. One will be t = 0, the other will be a t > 0. The t = 0 solution is the moment the ball is kicked from the ground. The t > 0 solution is the moment the ball hits the ground on the way down. Find the t > 0 solution to the equation above and that will be the answer you seek.