I'm trying to find the system of equations describing a frictionless planar pendulum (of known mass and length) that has it's pivot point fixed to the edge of a rotating disk (angular speed $\omega$). The pivot's position on the disk edge is such that the pendulum swings in a plane tangent to the disk.
I interpretted the motion of the pendulum to be:
As the disk rotates, the pendulum moves with the disk's rotation and it moves in a plane perpendicular to the disk's motion. So if you look at the disk from above, you'd see the pendulum spinning around the disk's edge, but also it'd be moving up and down, relatively, so that you'd see it pop up into the disk's plane, then drop down to be perpendicular to the disk.
I can't figure out where to start. Any help would be greatly appreciated.