h = 20 + .4 t - 4.9 t^2
solve for t when h = 0 just like the problem you posted below this one.
also the speed when it hits the ground is the same method.
A helicopter rises vertically with a constant upward acceleration of 0.40 m/s2 . As it passes an altitude of 20 m, a wrench slips out the door.
A) How soon does the wrench hit the ground?
B) At what speed does the wrench hit the ground?
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