The Tenser's Floating Disk spell creates a platform that can hold a maximum amount of weight above the ground, following you (if it can) when you get more than 20ft away from it.

An interesting portion of the spell is that the disk will vanish if too much weight is put on it. Now, let's say that a wizard with this spell has a very, very high running speed. Let's say that his disk is loaded with a ram that weights very close to the disk's maximum, but not more than it. Let's say that the speedy wizard runs at his highest speed (let's say, 200ft per turn) towards a wall, followed by his "ram-on-disk", then, very close to said wall, the speedy wizard throws something at his disk to add to its total weight in order to go over its maximum, thus making it vanish.

Considering that the now mid-air ram was going at a pretty high speed (thus having a big momentum), will it continue its trajectory towards the wall (it is implied that the wizard will duck), and if so, can it damage said wall with its momentum ? The question also applies for any target (buildings, creatures, etc.).

So, two questions here : 1) Does the object continue its trajectory or just falls to the ground with no momentum ? 2) If it continues, does it damage stuff that it bangs into ?

Please note that I'm searching for an answer supported by the rules (I don't know if there are any rules related to momentum and/or collision). If really none exist, then yes, my question should be closed, and I'll be happy to oblige.

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    \$\begingroup\$ Mixing physics with magic usually doesn't work well. This is very unlikely to be covered by rules so it will always be a DM ruling so I don't think an answer to this question has any benefit to anyone. \$\endgroup\$ – nwp Aug 18 '17 at 13:44
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    \$\begingroup\$ Well, answers to this question will have a benefit to eventual DMs who, confronted by this situation, will wonder what would be the best/most logical solution. The closest I can think of rules-wise is the falling damage rule, but it's indeed far-fetched. \$\endgroup\$ – Gael L Aug 18 '17 at 13:48
  • \$\begingroup\$ ...Well then. I see that the community really hates this question. Oopsies ! I'll try to be a good boy next time. \$\endgroup\$ – Gael L Aug 18 '17 at 14:08
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    \$\begingroup\$ @GaelL the community doesn't have feelings. The Q&A have to have a minimum objectivity, that is why the question got closed. The maximum speed of a floating disk is unknown, for one. \$\endgroup\$ – Mindwin Aug 18 '17 at 20:00
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    \$\begingroup\$ Lazily carrying treasure on the Disk while laughing at the poor fools physically carrying their treasure could be considered offensive. Oh, you meant... ;) \$\endgroup\$ – Ghotir Aug 21 '17 at 15:11

Even if it works, your speedster wizard has to run at around 278ft a turn for the ram to even touch the gate, let alone hit it effectively (without counting air friction).

For a horizontally thrown object:

$$ D=vt $$

Where \$D\$ is Distance travelled, \$v\$ is intial speed, and \$t\$ is time travelled, which can be calculated with the expression: $$ t = \sqrt \frac{h}{(0.5)g} $$ Where \$ h \$ is initial height and \$ g \$ is acceleration

From the description of the spell:

floats 3 feet above the ground [...] it remains within 20 feet of you

So \$ h = \$ 3 ft. and it has to travel at least 20 ft.

$$ v = \frac{20 ft.}{ \sqrt( \frac{3 ft.}{(0.5)(32.2) ft/s^2}) } \approx \mathrm{278 \, \, ft./turn} $$

If the ram is only allowed to descend 1 ft, it raises to 481.5 ft/turn.

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    \$\begingroup\$ Such a speed is entirely possible to reach for a PC. See rpg.stackexchange.com/questions/58632/… \$\endgroup\$ – Gael L Aug 18 '17 at 14:02
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    \$\begingroup\$ @GaelL You cannot enact the last part of your cunning plan at that speed. Wind walk is out as you cannot throw the pebble. You will need to use at least an action to make the throw and I as the GM would ask for at least a Dodge action to get out of the way (you have 0.25 seconds). That leaves you with a land speed of 420ft/turn. \$\endgroup\$ – Szega Aug 18 '17 at 14:13
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    \$\begingroup\$ OK, let's say that a friendly character is standing by to throw the object at the disk. In that scenario, all the speedy wizard has to do is to turn left/right at the last moment to not bump into the wall himself. \$\endgroup\$ – Gael L Aug 18 '17 at 14:14
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    \$\begingroup\$ @GaelL Not to mention that speed assumes you are shapeshifted as a storm giant. In which case just pry the door open with your hands. \$\endgroup\$ – Szega Aug 18 '17 at 14:15

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