At what time, t, will an object thrown vertically upward at 30 m/s reach its maximum height? (Take g = 10 m/s²)

At maximum height, v = 0. Using v = u + at with u = 30, a = −g = −10: 0 = 30 − 10t → t = 3 s. The object spends 3 s going up and another 3 s coming back to the launch point (total flight time 6 s).