From her bedroom window a girl drops a water-filled balloon to the ground, 4.77 m below. If the balloon is released from rest, how long is it in the air?

We need to use the equation x = vt + (1/2) at^2. We know x = 4.77, v = 0, and a = 9.81m/s^2. Plug in the values. 4.77 = (0) t + (1/2) (9.81) t^2 Solve for t. 4.77 = (4.905) t^2 0.972 = t^2 t = (sq. rt) _/0.972 t = 0.985 So it's in the air 0.985 seconds.