Water & Dimension Door (2nd Ed) Physics Question
Dan
happen:
If one places one half of a Dimension Door (the 2nd Edition version where
an actual portal is created) at the bottom of a body of water and the other
half (the "other side") of the D-Door above the surface of the water, would
water pour out the top? Would the orientation (horizontal vs. vertical) of
the doors be relevant?
Thanks,
Dan
Drew Id
"Dan" <druegar.a...@earthlink.net> wrote in message
news:9vkcbt4pbkg9tu0nq...@4ax.com...
> This came up in our game yesterday and I didn't know what would "really"
> happen:
>
> If one places one half of a Dimension Door (the 2nd Edition version where
> an actual portal is created) at the bottom of a body of water and the
other
> half (the "other side") of the D-Door above the surface of the water,
would
> water pour out the top?
Yes. Even if the submerged door is just below the surface, the water
pressure would force the water through the door.
>Would the orientation (horizontal vs. vertical) of
> the doors be relevant?
Only in determining *what direction* the water comes out. Even if the door
is horizontal, the water pressure from the submerged door will cause the
water to spout out of the "dry" door like a fountain (or at least like an
overflowing tub if the submerged door is not too deep).
Matt Lathrum
says...
Er, wouldn't that be relatively nasty if you cast a door in the middle of
the ocean? :)
Donovan Hawkins
Dan <druegar.a...@earthlink.net> wrote:
>If one places one half of a Dimension Door (the 2nd Edition version where
>an actual portal is created) at the bottom of a body of water and the other
>half (the "other side") of the D-Door above the surface of the water, would
>water pour out the top? Would the orientation (horizontal vs. vertical) of
>the doors be relevant?
Both the 2E and 3E Dimension Door describe instantaneous travel, not an
actual portal, and Phase Door only works for the caster (so not water).
However, I'll give you my opinion on a generic portalling spell (sorry in
advance if this turns into a physics treatise!).
If you put the exit portal 50' above the entrance portal, would you expect
the PC to have to exert the effort of climbing 50' during transport? If
the exit were 50' below the entrance would you give them falling damage?
If not, then you'd have to rule that the portal adds/subracts the
appropriate potential energy during transport. For definiteness I would
state this as the kinetic energy of each part of the person/object
transported is the same after as before.
Assume that each portal (entrance and exit) has a "front" and a "back"
such that material can only enter the front of the entrance, and it is
ejected from the back of the exit. Define that all orientations are
relative to the front (so up means the front is pointed up, side means
it's pointed horizontally, etc.). Be careful, because this means that you
exit in the opposite direction of the exit gate orientation.
If the entrance orientation is the same as the exit then you have no
problem because the person/object will be going in the same direction
after as before. If the orientation is different, should the person have
the same velocity but in the new direction? If not, it may not be possible
to pass through if the entrance has the opposite orientation of the exit
(you would be "ejected" towards the exit instead of away). So I would rule
one of two things:
1) Velocity now points in the appropriate direction. If the exit gate is
"up", then the new velocity will be "down" (you exit through the back).
2) Force the exit and entrance orientations to be the same.
Either way, we can assume that IF the orientations are different, then the
new velocity will point out of the back of the exit gate (opposite the
exit gate orientation). Whether this is allowed is the only question. Note
that if you fell into an "up" entrance with a "down" exit, you would be
thrown back up with the same velocity you fell with. A magic trampoline.
When underwater, the pressure is the thing that will force water into a
portal, and it is equal in all directions. Thus an underwater entrance
will pump water to a dry (above water level) exit. If the exit is oriented
"up" then the water will pour out of it (downward) as quickly as would a
same-sized hole on the bottom of a water tank whose depth was equal to the
depth of the entrance portal.
If the exit is oriented "down" you would expect the same amount of water
to be pushed up and out of the exit gate. How high it would shoot would
require calculation, but the build-up of water on the top of the exit gate
shouldn't slow the flow unless the pressure there were relayed to the
entrance. Since the gate is one-way, that isn't a problem. If the gate was
two-way, then the water would slow a little. Under no circumstances could
you get a still pool of water up there (unless the exit gate were enclosed
in a pressurized vessel).
Of course, you could rule differently if this creates a problem (there are
many things that violate physics in DND). You certainly should not allow
your characters to know this without experimenting.
Note that a permanent setup like this would be a perpetual motion machine
(you could run a water wheel indefinately). If you want a physics way out,
rule that there is a constant resistance when entering the gate which
keeps out strong winds and reasonable water pressures, but that any person
can overcome. Not that the PCs will know this, just the players.
Hope I didn't bore you to death (Save vs. Physics).
--
Donovan Hawkins "The study of physics will always be
Department of Physics and Astronomy safer than biology, for while the
University of California, Irvine hazards of physics drop off as 1/r^2,
haw...@uci.edu biological ones grow exponentially."
Drew Id
"Donovan Hawkins" <haw...@grad-ea-6.oac.uci.edu> wrote in message
news:995r5k$qlt$1...@news.service.uci.edu...
> In article <9vkcbt4pbkg9tu0nq...@4ax.com>,
> Dan <druegar.a...@earthlink.net> wrote:
>
> >If one places one half of a Dimension Door (the 2nd Edition version where
> >an actual portal is created) at the bottom of a body of water and the
other
> >half (the "other side") of the D-Door above the surface of the water,
would
> >water pour out the top? Would the orientation (horizontal vs. vertical)
of
> >the doors be relevant?
>
> (you could run a water wheel indefinately).
GMTA, I editted down my original reply, and in that reply, I had the line
"...and yes, this means you could make a perpetual motion machine, such as a
water wheel..."
For 3E, you could rule for a maximum volume of water to allow through such a
spell, based on similar volume-based spells of the same level. Creating a
large "flush" effect could probably be possible without being overpowered,
but not the draining of entire lakes or oceans, unless you want to allow
such effects.
Barry Smith
>
> This came up in our game yesterday and I didn't know what would "really"
> happen:
>
> If one places one half of a Dimension Door (the 2nd Edition version where
> an actual portal is created) at the bottom of a body of water and the other
> half (the "other side") of the D-Door above the surface of the water, would
> water pour out the top?
Well, that depends if one rules that the instantaneous duration of
Dimension Door would allow the door to remain open when the caster steps
through, or if it immediately closes behind him. If the former, the mage
just created a Decanter of Endless (salt) Water and is in serious
trouble by doing so. If the latter, the mage is going to end up getting
very soaked by the torrent of water that follows him through the DD.
Note the spell says that up to "500 lb." of non living matter can be
transferred via Dimension Door. Whether you rule that it is mandatory or
optional by the mage is for each DM to decide, but I'm inclined to rule
that opening a Dimension Door underwater won't cause a torrent of water
to erupt from the other end *unless* the mage steps through the doorway.
"Holding the door open" by placing something between the doors is
something I don't allow, and egress is usually only one way. To return
to the place the mage just left requires a second Dimension Door.
Would the orientation (horizontal vs. vertical) of
> the doors be relevant?
No, but placing a Dimension Door on a vertical axis that is high up in
mid air will cause anything traveling through to fall once they reach
the other end. Placement of a Dimension Door to climb a 80' cliff is
acceptable, however, if the end point is on solid ground.
--
Long live 2e.
Daniel Marshall
Donovan Hawkins wrote:
> In article <9vkcbt4pbkg9tu0nq...@4ax.com>,
> Dan <druegar.a...@earthlink.net> wrote:
>
> >If one places one half of a Dimension Door (the 2nd Edition version where
> >an actual portal is created) at the bottom of a body of water and the other
> >half (the "other side") of the D-Door above the surface of the water, would
> >water pour out the top? Would the orientation (horizontal vs. vertical) of
> >the doors be relevant?
>
> Both the 2E and 3E Dimension Door describe instantaneous travel, not an
> actual portal, and Phase Door only works for the caster (so not water).
> However, I'll give you my opinion on a generic portalling spell (sorry in
> advance if this turns into a physics treatise!).
Uh, huh...
>
> If you put the exit portal 50' above the entrance portal, would you expect
> the PC to have to exert the effort of climbing 50' during transport? If
> the exit were 50' below the entrance would you give them falling damage?
> If not, then you'd have to rule that the portal adds/subracts the
> appropriate potential energy during transport. For definiteness I would
> state this as the kinetic energy of each part of the person/object
> transported is the same after as before.
Right, go on...
>
> Assume that each portal (entrance and exit) has a "front" and a "back"
> such that material can only enter the front of the entrance, and it is
> ejected from the back of the exit. Define that all orientations are
> relative to the front (so up means the front is pointed up, side means
> it's pointed horizontally, etc.). Be careful, because this means that you
> exit in the opposite direction of the exit gate orientation.
Of course...
>
> If the entrance orientation is the same as the exit then you have no
> problem because the person/object will be going in the same direction
> after as before. If the orientation is different, should the person have
> the same velocity but in the new direction? If not, it may not be possible
> to pass through if the entrance has the opposite orientation of the exit
> (you would be "ejected" towards the exit instead of away). So I would rule
> one of two things:
> 1) Velocity now points in the appropriate direction. If the exit gate is
> "up", then the new velocity will be "down" (you exit through the back).
> 2) Force the exit and entrance orientations to be the same.
Obviously.
>
> Either way, we can assume that IF the orientations are different, then the
> new velocity will point out of the back of the exit gate (opposite the
> exit gate orientation). Whether this is allowed is the only question. Note
> that if you fell into an "up" entrance with a "down" exit, you would be
> thrown back up with the same velocity you fell with. A magic trampoline.
Well, sure...
>
> When underwater, the pressure is the thing that will force water into a
> portal, and it is equal in all directions. Thus an underwater entrance
> will pump water to a dry (above water level) exit. If the exit is oriented
> "up" then the water will pour out of it (downward) as quickly as would a
> same-sized hole on the bottom of a water tank whose depth was equal to the
> depth of the entrance portal.
Right...
>
> If the exit is oriented "down" you would expect the same amount of water
> to be pushed up and out of the exit gate. How high it would shoot would
> require calculation, but the build-up of water on the top of the exit gate
> shouldn't slow the flow unless the pressure there were relayed to the
> entrance. Since the gate is one-way, that isn't a problem. If the gate was
> two-way, then the water would slow a little. Under no circumstances could
> you get a still pool of water up there (unless the exit gate were enclosed
> in a pressurized vessel).
Pressurized vessel, you say...
>
> Of course, you could rule differently if this creates a problem (there are
> many things that violate physics in DND). You certainly should not allow
> your characters to know this without experimenting.
Certainly!
>
> Note that a permanent setup like this would be a perpetual motion machine
> (you could run a water wheel indefinately). If you want a physics way out,
> rule that there is a constant resistance when entering the gate which
> keeps out strong winds and reasonable water pressures, but that any person
> can overcome. Not that the PCs will know this, just the players.
Of course not.
>
> Hope I didn't bore you to death (Save vs. Physics).
Hope is a wonderful thing. Misplaced, in this case, but wonderful nonetheless.
:)
Xelloss
This brings up an interesting idea:
Put one side (the 'entrance') of the D-door on the bottom of the deepest
ocean, and the other directly in front of a foe. How does one calculate
the damage from that kind of pressure?
--
=================================
Xelloss Metallium.
Love him or hate him, he's still _there_.
(I bet you really wish life had a killfile, huh?)
"I can picture in my mind a world without war, a world without hate.
And I can picture us attacking that world, because they'd never
expect it." -- "Deep Thoughts" by Jack Handey
Tom Garnett
> ocean, and the other directly in front of a foe. How does one calculate
> the damage from that kind of pressure?
Start from the decanter of everlasting water, and scale it. Applying as much
physics/game balance/common sense as you want, in whatever combination you
want.
Do note the rather limited range though (IIRC).
--
Tom Garnett
Sir Bob
news:3AB6FC3C...@home.com...
I seem to recall reading somewhere that given the pressure of
water at the bottom of the ocean, coming into contact with a
"wall" of water subject to similar pressure would be akin to
walking smack into a cement block. Can't for the life of me
remember where I read it, though...
- Sir Bob.
P.S. Nih!
Dan
Hawkins) wrote:
>Both the 2E and 3E Dimension Door describe instantaneous travel, not an
>actual portal,
In the situation where this came up, we were using the psionic version (2nd
Ed) of Dimension Door which does create a visible portal. I didn't mention
it originally because I didn't want to accidentally start another "psionics
suck" thread....
>However, I'll give you my opinion on a generic portalling spell
Mercy buckets! ;-)
<excellent explanation snipped>
>Hope I didn't bore you to death (Save vs. Physics).
Not at all! Thank you very much for your expertise.
Dan
Peter Newman
> > Er, wouldn't that be relatively nasty if you cast a door in the middle of
> > the ocean? :)
>
> This brings up an interesting idea:
>
> Put one side (the 'entrance') of the D-door on the bottom of the deepest
> ocean, and the other directly in front of a foe. How does one calculate
> the damage from that kind of pressure?
Use the falling damage rules. You'll need to know the weight
and speed of the water. Calculating the speed of the water
may be difficult.