A dragonfly, at rest on a bullrush, decides to fly to a second bullrush 18 m away. It accelerates uniformly to a speed of. 5 m s-1, then immediately decelerates uniformly to rest on the second bulrish. Howlong the journey took?
The average speed is 2.5 m/s, both accelerating and decelerating. So it is 2.5 m/s for the whole trip.
The elapsed time is the distance divided by the average speed, or 18/2.5 = 7.2 seconds