Hi guys, I'm fairly new to the forum, so I don't know whether a similar question has been posted or not, but here's my question. If a box is being lowered at a constant velocity, is there work done on the box. My understanding tells me that since W=ΔEk+ΔEp, work done on the box is equal to mgΔh. If this is correct, then how can one explain the cause of this work? It seems a bit confusing because there is no net force acting on the object, and yet there's still work done. If possible, can you guys back up your reponse with reliable sources. thanks.