[pugio]

When I was a kid I had a character that could fly. I realized that a Decanter of Endless Water put out a pretty powerful constant thrust. Then a Helmet of Freedom of Movement could be interpreted to remove all excess friction due to win resistance (forget the details but it was something about removing any factor that would inhibit your movement). Constant acceleration and no friction... Unlimited speed.

I actually sat down and worked out all the equations based on the mass of my character and the amount of thrust the decanter provided. Our party would be deep in the wilderness somewhere and I'd say " I nip back to town to pick up some supplies, with acceleration and deacceleration it takes me 17 minutes".

Looking back, I think I was a pretty annoying player, but my DM was very patient. I guess he could see I put a lot of work into the scheme. It was also probably the most exciting application of physics I had encountered in my life so far.

[gridspy]

I think your DM might have changed their tune had you used an OP shield and turned yourself into a flying projectile.

It sounds like your cool application of physics was interesting and harmless. Good on you and your DM for making it part of the fun at the table.

[robocat]

https://www.dndbeyond.com/magic-items/4615-decanter-of-endle...

abridged: speak the command word "Geyser" produces 30 gallons of water that gushes forth in a geyser 30 feet long and 1 foot wide. As a bonus action while holding the decanter, you can aim the geyser at a creature you can see within 30 feet of you. The water stops pouring out at the start of your next turn.

Doesn't seem like the decanter has thrust. To design something that thrusts would require your character to have a deep understanding of D&D physics (or maybe just some deadly experimentation?!)

Trying to mix mundane physics and universe book rules (i.e. peasant railgun) in a D&D universe sounds like a dangerous pastime for a character.

Cue the old SF story where Hitler wants to control a portal to other planets. Version 1 destroyed when other end moved into a red sun creating a radioactive lance, Version 2 destroyed when other end put into an ocean creating high pressure hose.

Do you want your character to magically refine Plutonium, Madame Curie?

[pugio]

I said "as a kid" - I am not so young as to have played D&D 5e as a child.

I was referring to 3e, when the "simulation" aspect of the game was more heavily emphasized. See: https://www.dandwiki.com/wiki/SRD:Decanter_of_Endless_Water

> “Geyser” produces a 20-foot-long, 1-foot-wide stream at 30 gallons per round. ... The geyser effect causes considerable back pressure, requiring the holder to make a DC 12 Strength check to avoid being knocked down.

It was that last line that initially sparked the idea. Given the stated effects, this didn't seem like so much of a physics+rules stretch. The no-friction freedom of movement may have been more beyond the pale. Unfortunately 5e deliberately tried to close all the fun ways one could abuse various items.