Question

I'm not looking for answers, but I am at odds with 2 mechanics processes.
Example: an object is projected vertically at a velocity of 15m/s from point A, which is 20m above the ground.

The Question is asked: How long after release does the object hit the ground?

The questioner used s=ut+1/2at^2 right off the bat.
I instead, calculated the upward flight time, then used sqrt of 2h/g for the downward fall time and added them.

The two answers come out different. Why? Thanks

Charlie

Answer 1

the ground is 20 m below the starting point

Answer 2

Thanks R_scott, but I calculated t for point A to top of flight, then calculated top of flight all the way to the ground, then added them. Should they be the same then?