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