How much (if any) force does Tenser's Floating Disk transfer to ground?

Question

One question here is asking "What counts as ground for Tenser's Floating Disk?". The query seems aimed at using levitative powers or effects on whatever object the Disk is floating above.

Since certain powers are limited by weight capacity, this brings up the question of how much weight is applied to the object underneath the disk.

For example:

The lowest maximum capacity (Arcana check of 9 or lower) for Tenser's Floating Disk is 250 pounds. The maximum carrying capacity of Far Hand is 20 pounds.

Could someone use Far Hand to lift/move an object underneath a 250-pound-full Disk, and through doing so lift/move the Disk itself? How about the same, where the Disk is filled to its full upper limit (Arcana Check of 40 or more) of 2,000 pounds?

Or, how about a different situation. A Riding Horse has a maximum towing capacity of 1,312 pounds. Could it tow a cart that contains a fully-loaded one-ton Floating Disk?

Or, perhaps an unstable surface? Say the support structures under a certain surface will only hold up to 500 pounds before collapsing. What happens when one-ton full Floating Disk crosses over this surface?

Answer 1

I think the usage of the word "ground" in the description is meant to be interpreted in the same kind of way "ground" is interpreted in electrical circuits - as an effectively infinite source of upward force. Thus, Tensor's Floating Disk would be assumed to transfer exactly as much weight as is on it to the ground below it.

Its value is not in being able to negate the force/weight of stuff on it, but in being able to move it and to cushion the effects of the movement to things on it.

Thus, Far Hand wouldn't work. The unstable roof wouldn't work. The horse would.

Answer 2

None. The fundamental assumptions behind D&D 4e are not about realism drawn from the game world; they've simplified the game by making the rules come first. So the answer is "none..." You know where the ground is, so it hovers above the ground, regardless of interesting physics tricks. You have to treat it like Magic: The Gathering or whatnot, descriptions like that are for flavor not effect.

By the pure game rules, Tenser's Disk doesn't "exert force" - it is just there, and takes X amount of load. Far Hand doesn't "exert force" or "move the ground" - it can just lift a small object. You could surround a TFD with 100 Far Hands above below and sideways but it doesn't matter. It doesn't collapse a house. A horse doesn't need to exert any load to carry it, because it can't be carried or moved at all - it ONLY moves with the caster/by the caster's command per the spell description. The horse could haul the caster, and be burdened by the caster's weight, or not, but there is no meaningful way in which the horse can interact with the disk.

A TFD, by the rules, can ONLY be moved by it moving with the caster or at his command. It doesn't matter it the force of gravity goes to zero or dragons are tugging on it or whatever else you want to posit.