it is easy.
change
Pos x to variable y
same for the Particle Set
Pos X to variable motiony
check it out to attached gif [img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=2303.0;attach=4458;image[/img]

to get uniform motion, set acceleration a =0

btw
andresgo is from Facebook!
he sort of find https://www.facebook.com/pages/Easy-Java-Simulation-Official/132622246810575 and i directed him here.
easily to collaborate and learn with ability to attach xml