Why is a configurable joint/ArticulationBody moving both parts?

Unity Engine
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1

Video below to make the case more clear. Joint is moving both parts, parent and child with actual joint set.
c62sib

I want that only the child with the joint set is effected by “target velocity”, but I can not find such settings to do so. If I set parent to Kinematic or Immovable, it kind of gives the ~result I want, but that is not really an option.

Here are my settings:

1214×581 61 KB

And hierarchy:

Same thing for Configurable Joint with RigidBody

2

That’s correct. It’s the Newton’s third law, or “action-reaction principle”.

Increasing the mass of one of the parts will make that part move less than the other. The more the mass difference, the less motion in the most massive part.

Alternatively you may multiply the inertia only by some factor (Rigidbody.inertiaTensor). That will make that part rotate less.