Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site ucla-cs.ARPA Path: utzoo!watmath!clyde!cbosgd!ihnp4!mhuxn!mhuxr!ulysses!allegra!bellcore!decvax!ittvax!dcdwest!sdcsvax!sdcrdcf!trwrb!trwrba!cepu!ucla-cs!mccolm From: mccolm@ucla-cs.UUCP Newsgroups: net.games.frp Subject: Re: Physics in AD&D (Enlargements, etc.) Message-ID: <5464@ucla-cs.ARPA> Date: Thu, 16-May-85 15:25:20 EDT Article-I.D.: ucla-cs.5464 Posted: Thu May 16 15:25:20 1985 Date-Received: Wed, 22-May-85 07:51:36 EDT References: <401@ttidcc.UUCP> <276@wuphys.UUCP> Reply-To: mccolm@ucla-cs.UUCP (Eric McColm) Organization: UCLA Computer Science Department Lines: 76 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 honk,honk..beepbeepbeep..blatt..hooga--!..paaaaaaaaaaaaaaaa* (looks like a 'hole lot of folks 'round here love Shiva ev'ry mornin')