Question 209373
Since 'S' is the "height above the ground", set it to zero and solve for t:
S = - 16t^2 – 32 t + 128
0 = - 16t^2 – 32 t + 128
Divide both sides by -16:
0 = t^2 + 2t - 8
Factoring the right:
0 = (t+4)(t-2)
t = {-4, 2}
We can throw out the negative solution leaving:
t = 2 seconds