i have some model here that u can change to want u want

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1840.0

a car rolling down a slope and colliding with bumper with coefficient of restitution e = 0.2
http://weelookang.blogspot.com/2010/06/ejs-open-source-multi-objects-rolling.html
https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_Car6web.jar
author:Ejs Open Source Rocket Car on an Inclined Plane Java Applet is by Wolfgang Christian, Francisco Esquembre, and Mario Belloni using the Easy Java Simulations (Ejs) modeling tool, now remixed by lookang

enjoy!