Imagine a door made out of butter and a "whip" made from a handle, 2m of very hot wire and a little piece of something that's is cold and is used as a weight (like a little sphere of half an inch diameter for example).
You hold the handle and "throw" the weight at the door (for example by making a sudden move with the handle in direction of the butter door).
The weight is cold and cannot go through the door, but some of the hot wire will cut through the door like a hot knife through butter. Depending how far away from the door you are, there will some length of wire that will form a loop partly on the other side of the door and you can move that loop a little and cut further, before the wire finally just hangs down because of its own weight and the weight of the littly sphere.
Important is, that a certain length of wire will travel through the door and the weight at the end does not, so in some shape or the other, there will be a cut in the butter door.
This is not the normal whipping motion and it depends very much on how much resistance the door gives and how "hot" the wire is, to determine if you think that a monowhip can cut holes into a door. If you think the door's resistance is quite high and the wire's own weight is very low, then the wire will be stuck in the door.
If you think monowhip can cut through literally anything without resistance, then the wire is extremely hot and will go through and make a loop and can cut a hole.
Choose what you want for your campaign. I personally like the idea of 4th edition, that I can damage the door, but only for 1 damage with each swing (the loop cutting little holes).