# If I have a chain of segments that only move on a 2D plane, and I want to know how they move when a “muscle” applies a torque on a joint, I need forward dynamics, right? Where can I learn more of it?

Hi, sorry for the gore title, I’m currently working on a software simulation that involves a chain of segments (bones) on a 2D plane, and two muscles attached (one in each side of the joint). Something like this, there each small rectangle is a “bone”, they are attached to each other by joints, and the red lines are the muscles, as I said, there are only two per joint (one to flex and the other one to extend). I understand that a software simulation is maybe not robotics so maybe I’m in the wrong subreddit, but from what I understand this type of math is mostly used in the field of robotics.

What I want to do is: given the contraction of one of those muscles, how will the chain of segments move? Additionally, the distal end of the most distal segment may be fixed, so I assume the big body (the big rectangle) could move too.

So, I’m not sure what math do I need to calculate all that, I looked for forward and inverse kinematics but they don’t bother much with forces, just with position. I think that what I need is forward dynamics, but I can’t find much of it from zero. Everything that I find is all a bit too complex from the get go, I wanted to know if there is some actual basic documentation for starters. I have some notions of matrices and I can work fine with trigonometry, so I don’t mean those basics, but the basics of forward dynamics. Or maybe I’m wrong and I don’t even need that and it’s something else…

submitted by /u/MartinaS90