Is there any way to establish temporary joint in Gazebo while using URDFs? Or simply 2 joints with no movement constraint between them but such that they can collide with each other? I tried using floating joints but the problem is that collision between them nullifies. I don't want this to happen.

Basically I'm trying to accomplish a pick and place task. A model has a stand on which the object is hanging. I just need to remove it and drop it on the ground. Any solutions to this?

NOTE - I can only use URDFs and not SDFs I'm using Gazebo-9, Ubuntu 18.04, and ROS Melodic