Can you push Tenser's Floating Disk so that it doesn't just hang out behind you? If so, how hard would it be to push?
RAW, the text of the spell says "No":
The disk is immobile while you are within 20 feet of it.
Immobile is pretty clear (emphasis mine).
That said... I don't see any reason why a DM should not allow the spell and its cargo to be moved around at the expense of an action by the caster.
Immobile could mean it stops moving on it own. It could mean nothing can ever move it.
This really is not something the RAW answers. No amount of interpretation will make this clear. There is no way of parsing this that will be immune to abuse.
If you take immobile to be an absolute you've just given the player an immovable object to counter the DM's irresistible force. They could stop a charging dragon with one of these and build a cage with three of them.
So don't think being conservative with how you read a spell makes it immune to abuse.
Tenser's floating disk is fun because you can invent uses for it. A DM that insists the only use is to escape the encumbrance rules is running a poor game.
The best way to answer this question is to go buy a scroll of Tensor's Floating Disc. Use it. Give the disc a push. See what happens. Now decide if you want to learn the spell.
The caster cannot push the disk to cause movement, but an outside party May be able to.
The Disk has a force of 500 pounds, after which it fizzles. If the disk comes to an impassable obstacle, then it either:
- knocks it out of the way (if it can, with it's remaining force)
- stays in place.
Let's analyze the former. With this AI in place, if the disk leaves 20 feet, then an outside party can push the disk, so long as the pushing doesn't overburden the 500 pounds. 2 strong men could overburden the disk, causing it to fizzle. The disk, however, cannot be moved.
The later means that so long as an obstacle remains in front of it (eg: a fence) the outside force could easily tow the disk in any direction (except up/down).
While inside the 20 foot radius, nothing can move the disk, only fizzle it.
If your goal is to abandon the disk, all you need to do is trap it with a material that's > 10 feet tall, and can take a 500lb force without give (assuming the former rules), and walk away.