An object is thrown upward from the top of an 80ft tower. The height h of the object after t seconds is represented by the quadratic equation h = -16t^2 + 64t + 80.
After how many seconds will the object hit the ground?
29 seconds
6.4 seconds
5.0 seconds
8.0 seconds
To find out when the object will hit the ground, we need to find the value of t when h = 0.
So, we set h = 0 in the equation:
0 = -16t^2 + 64t + 80
Rearranging the equation:
16t^2 - 64t - 80 = 0
Dividing the equation by 16:
t^2 - 4t - 5 = 0
(t - 5)(t + 1) = 0
So, t = 5 or t = -1
Since time cannot be negative, the object will hit the ground after 5 seconds.
Therefore, the correct answer is:
5.0 seconds