Hi I am making physics engine (computer) and i have some problems with interpretating multiple forces on one body. http://img837.imageshack.us/img837/396/75i7i47i6.png [Broken] On the fourth car (on right) there are two forces acting on two rear wheels, interpretation is obvious, but what when only one force is acting ? Which of these three interpretation, if any, is correct? How to calculate how much force is moving body and how much it is rotating it (moment) ? I currently use second image interpretation but i think it is not correct. And, second question, how to calculate when mutiple forces with random angles etc are present ? I think somebody asked that question before: https://www.physicsforums.com/showthread.php?t=222598 but i don't understand answer he was given. I have force angles and forces, but i can have x and y components about any axis/angle. I need a way to calulate resultant force/moment.