Question W/unity provided IK system; a sphere and a rotating plane in 3d space; keep the sphere connected?

Using the Unity provided IK system with a sphere and a plane in 3d space. How could I keep the spear "connected" to the plane but respect gravity relative to the sphere?

For example, if the plain and sphere are orientated like


The sphere is "connected" to the ground with IK, and still under the influence of the built-in gravity.

Additionally, if the plane was rotated vertically (or any other position)

The sphere is still "connected" to the plane but is still affected by the built-in gravity.