For this case we have the following equation: h (t) = - 12t2 + 36t When the object hits the ground we have: - 12t2 + 36t = 0 We look for the roots of the polynomial: t1 = 0 t2 = 3 Therefore, the time it takes the object to hit the ground is: t = 3 s Answer: the time when the object hits the ground is: t = 3 s