
Asadaly J. answered 10/29/20
Experienced Teacher's Assistant Specialized in Writing and Mathematics
Hey Kishi!
Here, we're given a function and we're trying to find when y (the height) will be at 3 (the initial height), so let's plug in our values!
y = -16t^2 + v0t + h0
3 = -16t^2 + 30t + 3
0 = -16t^2 + 30t
16t^2 -30t = 0
t(16t - 30) = 0
t = 0 and 16t-30= 0
16t - 30 = 0
16t = 30
t = 15/8
So we know that the height is at 3 feet at 0 seconds and 15/8 seconds, but we rule out 0 seconds because that's the initial height. Therefore, our answer would be 15/8 seconds