Question

An object is thrown directly up (positive direction) with a velocity (vo) of 20.0 m/s and do= 0. Determine how long it takes to get to the maximum height of 24.0 m.

Answer 1

Vfinal is 20m/s because speed coming down is the same as going up, and v initial is 0 because we can assume that this problem is the same as a drop problem.

so 400 = 2(9.81)x
solve for x and it is about 21.

so now we have the maximum height reached.
use x=0.5at^2 to solve for time to fall.

21=0.5(9.81)t^2
4.3=t^2
time=2.17 seconds aproximately (sorry i had no calculator you may want to check the math but the formulas are right.)Source(