A stone is thrown upward from the top of a building at an angle of 30 degree to the horizontal and with an initial speed of 20m/s. The height of the building is 45m. How long is the stone "in flight"? Solution: Vx0 = 20cos30 = 17.3 Vy0 = 20sin30 = 10 -45 = 10t - 1/2 g t^2 t = 4.22s This is an example from my physics textbook. I wonder why the solution is in this way. Why the time used to reach the highest level and the time from the highest level to the initial position are not considered as time "in flight"? Thanks.