I have one static Item that i am trying to attach a round object too, when an item hits the round object I want it to move (slightly) then go back to its previous position kind of like a punch bag, I can't use gravity as the item to be hit is on top of the static item.

What joint would be best for something like this and how would you detect when to move it back to the original position?

Thanks

Maybe apply force on the "punchbag" or apply linear velocity based on the power/speed of the hit then reset it either based on the "punchbags' position or after a set period of time.

Could you use negative gravity? So kind of like a helium balloon on a string, if you punch it down it will float back up but stop when it reaches the length of the string. I think a chain of a couple pivot joints could simulate that, one end anchored to the static base and the other attached to the floating object.