[net.games.frp] Physics in AD&D

hollombe@ttidcc.UUCP (The Polymath) (05/07/85)

Here's a D&D physics question for you.  First, some background:

How to kill a beholder:

	1. Take a ballista bolt or two and have a  high-level  mage  shrink
	   them to crossbow bolt size.

	2. Use a heavy crossbow to launch them at the beholder.

	3. The beholder sees them coming, detects magic, and aims its anti-
           magic ray at them.

	4. The shrink is dispelled, the beholder is  hit  by  the  ballista
           bolts which do it a world of hurt.

My DM assures me that this technique, and variations on it,  are  the  only
sure method he's heard of safely killing a beholder.

Flaw:
The unshrunk ballista bolts have regained their full size and  mass  (never
mind where it was) but only have the kinetic energy of an ordinary crossbow
bolt.  They should fall out of the air before they get to the beholder.

The above, of course, assumes conservation of mass  and  energy.  The  real
question  is:  are these and other physical properties conserved in a world
where magic works?

(I know this is basically up to the DM, but it seems  like  an  interesting
topic for discussion).
-- 
-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
The Polymath (aka: Jerry Hollombe)
Citicorp TTI
3100 Ocean Park Blvd.
Santa Monica, CA  90405
(213) 450-9111, ext. 2483
{philabs,randvax,trwrb,vortex}!ttidca!ttidcc!hollombe

js2j@mhuxt.UUCP (sonntag) (05/09/85)

> Here's a D&D physics question for you.  First, some background:
> How to kill a beholder:
> 	1. Take a ballista bolt or two and have a  high-level  mage  shrink
> 	   them to crossbow bolt size.
> 	2. Use a heavy crossbow to launch them at the beholder.
> 	3. The beholder sees them coming, detects magic, and aims its anti-
>            magic ray at them.
> 	4. The shrink is dispelled, the beholder is  hit  by  the  ballista
>            bolts which do it a world of hurt.
> My DM assures me that this technique, and variations on it,  are  the  only
> sure method he's heard of safely killing a beholder.

     The really simple way, if you have enough room to manuver, is to simply
plunk arrows at them from 15" away or so.  The poor beholder has no useful
rays with ranges like that, and it can only go at 3"/rnd or so, so you have
plenty of time to move a little between shots to maintain the proper range.
It's always worked great for me.
-- 
Jeff Sonntag
ihnp4!mhuxt!js2j
    "A plot to takeover CBS was pushed today by some narrow-minded, manip-
ulative, right-wing, flaky conservatives who think their weirdo views aren't
being handled fairly by our more liberal and intelligent news staff!"

faustus@ucbcad.UUCP (Wayne A. Christopher) (05/10/85)

I think the best way is to sneak underneath one and then grab onto it
somehow from the bottom... Those eye's aren't too flexible.

	Wayne

mike@wuphys.UUCP (Mike Jones) (05/11/85)

> Here's a D&D physics question for you.  First, some background:
> 
stuff omitted
> My DM assures me that this technique, and variations on it,  are  the  only
> sure method he's heard of safely killing a beholder.
> 
> Flaw:
> The unshrunk ballista bolts have regained their full size and  mass  (never
> mind where it was) but only have the kinetic energy of an ordinary crossbow
> bolt.  They should fall out of the air before they get to the beholder.
> 
> The above, of course, assumes conservation of mass  and  energy.  The  real
> question  is:  are these and other physical properties conserved in a world
> where magic works?
> 
> The Polymath (aka: Jerry Hollombe)
First: Kinetic energy is not conserved in the "real" world.  Why should it be in
	D&D?
Second:  The real kicker is in "(never mind where it was)".  You postulate that
	mass is NOT conserved, then ask if it is.  A poor question.
Third: Magic need not follow the normal laws of physics.  It must be internally
	self consistent.  It is therefore much easier if it follows the (self
	consistant) normal physical laws. You then postulate that magic adds
	some currently unknown laws, or places, and try to follow the
	consequences logically.  In this case for self consistency we check the
	enlarge spell and see "a hurled stone would have more mass (and be more
	hurtful..."  That puts some interesting constraints on your physical
	system, but I covered that in Second.  Bottom line, it should work.
	Make the physics agree.

Mike Jones
Physics Dept. Washington University
ihnp4!wuphys!mike
(Back to my quantum necrodynamics text).

hutch@shark.UUCP (Stephen Hutchison) (05/14/85)

In article <862@mhuxt.UUCP> js2j@mhuxt.UUCP (sonntag) writes:
>> Here's a D&D physics question for you.  First, some background:
>> How to kill a beholder:
>> 	1. Take a ballista bolt or two and have a  high-level  mage  shrink
>> 	   them to crossbow bolt size.
>> 	2. Use a heavy crossbow to launch them at the beholder.
>> 	3. The beholder sees them coming, detects magic, and aims its anti-
>>            magic ray at them.
>> 	4. The shrink is dispelled, the beholder is  hit  by  the  ballista
>>            bolts which do it a world of hurt.
>> My DM assures me that this technique, and variations on it,  are  the  only
>> sure method he's heard of safely killing a beholder.
>
>     The really simple way, if you have enough room to manuver, is to simply
>plunk arrows at them from 15" away or so.  The poor beholder has no useful
>rays with ranges like that, and it can only go at 3"/rnd or so, so you have
>plenty of time to move a little between shots to maintain the proper range.
>It's always worked great for me.
>-- 
>Jeff Sonntag
>ihnp4!mhuxt!js2j
>    "A plot to takeover CBS was pushed today by some narrow-minded, manip-
>ulative, right-wing, flaky conservatives who think their weirdo views aren't
>being handled fairly by our more liberal and intelligent news staff!"

Since I don't play standard AD&D my suggestions might not be seen as real
close to the accepted standard, but I would think that any intelligent
creature with the power of a Beholder would set up a situation where there
would be no way for you to get close enough to shoot without it being also
close enough to shoot back.  Also, recall one of those eyes does telekinesis
and can be used to deflect arrows, to set off traps, to manipulate weapons
from a distance, etc.  Actually the best way to deal with a Beholder is
to use cunning, guile, and kamikaze effects.  In the case of one of my own
monster characters, a witch of some skill, she would write a symbol-spell
equivalent to Exploding Runes with a Conditional Detonation, roll the
parchment up and put it in a digestion-proof container, and feed it to a
charmed orc, kobold, etc.  The charmed critter would then be talked into
a battle frenzy and go after the Beholder, which would kill and eat the
bait.  It would then explode inside the body of the Beholder, some hours
later, as the protective container finally eroded away.

Hutch

mccolm@ucla-cs.UUCP (05/16/85)

In article <276@wuphys.UUCP> mike@wuphys.UUCP (Mike Jones) writes:
>> The unshrunk ballista bolts have regained their full size and  mass  (never
>> mind where it was) but only have the kinetic energy of an ordinary crossbow
>> bolt.  They should fall out of the air before they get to the beholder.
>> 
>> The above, of course, assumes conservation of mass  and  energy.  The  real
>> question  is:  are these and other physical properties conserved in a world
>> where magic works?
>> 
>> The Polymath (aka: Jerry Hollombe)
>
>First: Kinetic energy is not conserved in the "real" world.  Why should it be
>       in D&D?
> .....
>Third: Magic need not follow the normal laws of physics.  It must be inter-
>       nally self consistent.  It is therefore much easier if it follows the
>       (self consistant) normal physical laws....
>
>Mike Jones

If you want to try applying some sort of physics to the Enlarge spell, (and
to other shapechanging spells), you have four choices, as I see it:

1) Conserve Velocity across shape- and size-changes.  This is clearly what
   was intended in the AD&D joke books.  But this has a *real* serious
   problem:  let's suppose I shoot an arrow at someone, and then double all
   it's linear dimensions while in flight.  The 8 times more massive arrow
   does an average of 3.5*8=28hp, enough to drop a 6HD monster.  Not bad.

2) Conserve Momentum across shape- and size-changes.  This is even worse,
   because now the small rock that I throw and reduce by 70% will be
   travelling at near 200mph when it hits the target.  And polymorphing
   a charging dragon into a kobold can be humorous when the "kobold"
   digs into the side of a nearby hill at at least mach 1.  Remember to
   duck.

3) Conserve Kinetic Energy across shape- and size-changes.  This is appealing
   to me because kinetic energy is what causes damage in the absense of
   sharp objects.  So the 2kg brick thrown at 10m/s has a K of 10J.
   The .5kg hardball resulting from reducing the brick will be travelling
   at 20m/s, and the 20kg block resulting from *enlarging* the brick will
   travel at 3.1m/s, and all will have a K of 10J, and all will do 1D3 damage.
   But if an object is thrown *over* someone and Enlarged, it could fall out
   of the air onto the poor slob, doing damage based on how far it fell.
   Fortunately, it takes a Victorian physicist (at least) to hit the target.

4) Don't conserve any of the above, and make up something for yourself.
   A ref. in one campaign claimed that Enlarge made things "puffy" (mass
   was conserved).  This applied to inanimate things only, but it avoided
   many problems.  But that didn't mean I had to like it.  My character
   was a magician.
--fini--
Eric McColm
UCLA (oo' - kluh) Funny Farm for the Criminally Harmless
UUCP:  ...!{trwspp,cepu,sdcrdcf,ihnp4,ucbvax}!ucla-cs!mccolm
ARPA:  (still) mccolm@UCLA-CS.ARPA  (someday) mccolm@LOCUS.UCLA.EDU
Q1:  "The world is round.  The rest is up to us."
Q2:  "Reason is Peace, Fanaticism is Slavery; Tolerance is Strength."

mccolm@ucla-cs.UUCP (05/16/85)

In article <276@wuphys.UUCP> mike@wuphys.UUCP (Mike Jones) writes:
>> The unshrunk ballista bolts have regained their full size and  mass  (never
>> mind where it was) but only have the kinetic energy of an ordinary crossbow
>> bolt.  They should fall out of the air before they get to the beholder.
>> 
>> The above, of course, assumes conservation of mass  and  energy.  The  real
>> question  is:  are these and other physical properties conserved in a world
>> where magic works?
>> 
>> The Polymath (aka: Jerry Hollombe)
>First: Kinetic energy is not conserved in the "real" world.  Why should it be in
>	D&D?
>.....
>Third: Magic need not follow the normal laws of physics.  It must be internally
>	self consistent.  It is therefore much easier if it follows the (self
>       consistant) normal physical laws....
>
>Mike Jones
>Physics Dept. Washington University
>ihnp4!wuphys!mike
>(Back to my quantum necrodynamics text).

As I see it, when deciding this issue, you have four choices:

1) Conserve velocity across shape- and size-changes.  This is clearly what
   was intended by the AD&D joke books.  But this has a *serious* problem.
   Suppose I shoot an arrow at some poor fool, and enlarge all the arrows
   linear dimensions by 100% while it's in flight.  The 8 times as massive
   arrow now does an average of 3.5*8=26hp.  Enough to drop a 6HD monster.
   This assumes, of course, that the damage is related linearly to mass of
   the weapon, which for blunt weapons is reasonable, but for arrows...

2) Conserve momentum across shape- and size-changes.  This is appealing to
   modern physics-knowledgeable frpers, but it has even worse problems.
   If I throw a fastball at someone, and then Reduce it by 70% in midair,
   it now has 1/40th its original mass, with the same momentum.  That
   60mph fastball suddenly changes into a 1" diameter cannonball with a
   speed over mach 3.  One of my magicians used to slay charging dragons
   by polymorphing them into kobolds, with the result that they pile into
   the nearby hillside at better than mach 1.  The next spell my magician
   researched was teleport, for obvious reasons.

   This wouldn't be such a problem, except that even a level 1 magician can
   produce a 10% size change, giving 75% the original mass, and 4/3 the
   original speed.  This is enough to start adding damage.

3) Conserve kinetic energy across shape- and size-changes.  This is appealing
   to me, because I usually think of K as the cause of impact damage.  So
   if I throw a 2kg brick at 10m/s at some poor slob, K=.5*2*10**2=100J.
   But if I reduce it to a .5kg baseball, with K=100J, its velocity is now
   20m/s.  And if I enlarge it to a 20kg siege rock, its velocity is now
   3m/s.  So the damage done by a thrown or propelled object is constant
   the object is in flight.

   It is still possible to do silly things, however, by throwing the object
   over the target, enlarging it, and letting it fall on the luckless slob
   who really should have stayed in bed that day.  The damage is related
   to the distance it fell.  But it takes a Victorian era physicist to
   aim the rock to hit the target with any accuracy.

4) Ignore the above, don't conserve any of them, and make up something on
   your own.  One referee decided that Enlarge conserved mass.  That would
   quickly run afoul of Reduce making tiny dragons that sink into the ground,
   but it still sounds fun.

ps-For those of you who are annoyed with me for posting this twice and
cancelling the first one, consider that the first version began to evolve
into a new life form after I posted it.  I decided euthenasia was warranted.
--fini--
Eric McColm
UCLA (oo' - kluh) Funny Farm for the Criminally Harmless
UUCP:  ...!{ucbvax,cepu,ihnp4,trwspp,sdcrdcf}!ucla-cs!mccolm
ARPA:  (now) mccolm@UCLA-CS.ARPA   (someday) mccolm@LOCUS.UCLA.EDU

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