We put the acceleration of gravity, the initial velocity and the initial height all together to get our formula for height as a function of time:
y = -16t² + 8t + 24
We want to know when y=0
0 = -16t² + 8t + 24
0 = 2t² - t - 3
0 = (t + 1)(2t - 3)
t= -1 or t=3/2
We reject the negative root.
Answer: 1.5 seconds later
