On the following capx file (it is a capx, you can download it with the top button, google drive just recognize it as a zip file): https://drive.google.com/file/d/0B-Asjs ... sp=sharing
We have two objects, Blue and green, as well as 2 tiledbackgrounds (one is the ground, the other is ust here as a height reference), If you run the capx, and press the up arrow, both will elevate sort of the same height, and take about 6 seconds to end the jump (3 to go to the top of the red tiledbackground, and 3 others to come back to the ground)
However, Blue has a 200px/s initial speed and 66.6666 gravity, while green has a 33.3333 gravity.
Maths shows us that if the time to go up is T1, and the height of the jump is Y1, we have:
V1 the jump strength (aka initial speed in px/s): V1=2*Y1/T1
G the gravity (in px/s²) : Y1/(T1²)
So for a 300 px height, for 3 seconds to reach those 300px:
G=-100/3 px/s² (about 33.3333)
But the platform behavior with those settings won't produce that result, far from it, the "Gravity" seems actually to be the "Halved gravity" (visible on blue), but for green, which has its position setted manually, no issues, why is that? Is the platform behavior wrong by saying "Gravity in pixel per seconds per seconds"?
Edit:tl;dr, I was actually wrong, I have a corrected formula in a post below to get the jump strength and gravity for a wanted height and elevation duration
Game design is all about decomposing the core of your game so it becomes simple instructions.