Ive been trying to figure out how to calculate the hang time of a jumper. Im a bit confused because some of the formulas make no sense to me. One source says that 1/2 the hang time can be calculated with the following formula if the distance is given. t= sqr(2d/g) but wouldn't that use a constant velocity of g not taking into account the extra force exerted for the upward movement?

Just like if somthing is dropped it should fall at a velocity of 9.8m/s2 v = gt and if it is thrown down it shoud be v = vo + gt. So how can this source say that a vertical standing jump of 1.25m = 1sec?