# Homework Help: Dynamics: 3D kinematics

1. May 26, 2010

### steak313

1. The problem statement, all variables and given/known data

[PLAIN]http://img208.imageshack.us/img208/5445/problem3.png [Broken]

All problem info contained in the image.

2. Relevant equations

equations of relative motion?

3. The attempt at a solution

Frankly I am stuck on where to begin. I would normally make a free body diagram, but doing this alone doesn't seem to get me very far. I would also usually start making position vectors and work my way through velocities and accelerations point by point; however, those problems are always asking me to find velocities or accelerations at a particular point. This is asking for the reaction forces and moments at A and B. The way the picture looks makes me think the weight of the plate will be concentrated at the center and going vertically downward. Any hints on where to begin?

Last edited by a moderator: May 4, 2017
2. May 26, 2010

### steak313

Okay, so I was totally off before but I think I at least know whats going on now. I am pretty sure this problem will require euler's equations of 3D motion.

So the plate seems to rotate about the fixed points A and B. I will choose A as my origin. I then can make my inertial matrix for the plate and go on computing moments.

My first question is about point A; I can choose this point correct? The plate is rotating but I think point A is fixed relative to this motion. If not I believe the centroid of the plate should work as well. I must go to class shortly so I can not caluclate all of the matrices yet, but is this the correct approach? I believe I have the tools to solve the problem but some of the details are not quite clear.

Any input would be greatly appreciated! I will be back in a few hours.