Topic: Magic and Physics

[FatSteve]

I know this has probably been brought up before, but I can't really find a discussion thread that answers the question I have.  So here goes.  Perhaps there is someone out there who actually paid attention during Physics class.  I just wasn't that guy...

When reading the description of the Staying spells, they say the exert X pounds of "pressure" on an object, in one direction.  My rusty recollection of Physics tells me that Pressure is the force per unit area exerted by a liquid or gas.  It is usually described in pounds per square inch (PSI) or Newtons per sqare meter.  Or sometimes Dynes per square centimeter.  My question is how will this "pressure" affect moving objects?  Or, perhaps it is better to ask, "How does this apply to momentum?" 

An example:  I am a foolish spell user, and I should have seen it coming.  Trapped with no fighters to hide behind, I see my enemy on the nearby wall ready his heavy crossbow and take aim.  I know I cannot complete my Hard Wind spell in time to blow him off the wall, but I do have this simple, "Staying I" spell stored in my trusty staff.  I cast the Staying spell on the bolt, right before it is fired, and concentrate as it leaps from the bow toward me. 

Let us assume the following: 

1.  The bolt weighs half a pound.
2.  The crossbow has a 200 pound pull weight, and a "throw" of about 1 foot (the distance over which the string is accelerating the bolt). 
3.  I am 100 feet from the crossbowman.
4.  I am able to maintain concentration on the incoming bolt for the needed duration. 

The question, in its final form, is of course,  "Is it safe?" 

Steve

[markc]

 [My personal oponion not offical in any way.]
 IMO we are dealing with magic not physics so the spell staying I has not affect on the bolt. Staying I IMO should not have any bonus to DB, it should not stack with shield, missile adviodance or any other spell that provides DB.
 Also IMO if you used your example above and it did affect the bolt. It would only affect it once, not continually affect the bolt as it traveled towords you. If you did use a very very hard spell mastery on staying I to allow it to constantly effect the bolt I still do not think I would allow it as you would have to place the wall of the staying I effect directly in the path of the bolt. IMO that is almost impossible for a spell to do at instant speeds.

 Also your GM has the last word on how spells work in his game world. So he, she, they are the ones to ask if your idea has any legs to stand on or not. Again in my world I would say it has no effect.

MDC   

[Fornitus]

 As Markc said, depends on the GM. But, you asked, so for me and my group....

 Staying I applies 1 pound of force on a object. Removing the problem of whether the Guard gets a save for the item in their hand or not, the spell requires a target to work. If a GM alowed Saying I to work on air like a wall, it would just create a area of calm air with no real effect on the bolt.
 So with the bolt as the target, the spell would only drop the amount of force the crossbow is able to apply. Basicaly reducing the 200 pound throw weight by one pound of reistance.
 Since various crossbows are not exactly alike, a 200 pound pull will have a variation of a fue pounds either up or down anyway depending on age of the weapon, weather at the time of firing, craftmanship of the weapon in question, ect....
 
 The real spell your looking for is Telekinesis I. Staying specificaly (in RMC) wont move an object by itself. However, Telekinesis can lift the tip of the arrow an inch or so thereby compleately screwing up the arch of the shot. Or, if your GM is REALLY being nice, cause a fumble of the crossbow as if it was improperly loaded. (I am not that nice)

 Good Luck

[FatSteve]

I was really just using the arrow as an example of the concept I am trying to examine.  My impression of the Staying spell has always been something that was continuous.  For example, if you cast a higher-level staying spell on a fighter trying to get to you, he would have to continually press into that force as he moved in your direction.  If he were to turn around and move the other direction, he would move normally until he tried to come back your direction, at which time he would still find it difficult to move toward you.  He would not move "through" a "curtain" of the spell, and then have free movement; the spell would continually apply the force to him in a way that made it significantly more difficult to move in a given direction. 

As Fornitus said, the spell works on a Target, and there is no restriction that says the target cannot be an arrow or bolt.  (There are rules for Force spells and resistance rolls when the target is held by a person though.)  And since the spell focuses on a Target, that target should continue to feel the effects of the spell for the entire duration of the spell.  If the Staying is set to prevent the target from moving south, it doesn't matter how far east, north, or west the target moves, if the spell is still active, he should continue to have difficulty moving south. 

Since I am the GM of the game in question, the real point of this question is I like to have consistent reasoning behind the spells.  I realize the effect is magic, but since it causes movement (or inhibits movement) then some aspect of the "laws" of Physics should be able to describe what it is doing and allow me to apply that reasoning in other situations. That is what I am looking for.  I'm just wondering if someone already thought this one through, and if so, what did they finally decide?

Using the way the spell is described, the bolt would have to constantly overcome the "pressure" of 1 pound as it flew in the "prohibited" direction.  My tendency is to think that would cause the bolt to slow rapidly and not make it very far.  As for game balance, I realize that is not the intent of the spell, but it is also much slower to cast than something like Deflections (instant), and therefore not as useful for that application. 

FatSteve

[Winterknight]

You're correct in that pressure is a force exerted over an area, yet no area is defined.  When we consider the spell's limitations of a single direction, it seems apparent that the spell should instead be applying a force, not pressure.

But then, of course, the nerds could say, "Well, if a force of 1 lb is applied to a surface of any target, and my target is a dragon, then by reducing the size of the surface area to a human, I can increase the pressure and crush him!!"

It's a poorly worded spell, and open to interpretation, in that regard, IMO. 

Perhaps the spell's "real" effect is to increase the coefficient of drag sufficiently to produce a movement hindrance equivalent to X pounds of force.  This could be accomplished by binding molecules to the surface of the target, although that makes less sense with the single direction limitation. 

I guess I don't have an answer for you here.  GM's coin flip.

[markc]

 I just looked up the spell in RMSS Spell Law 95. I have allways used it as a wall type effect in that as soon as the person or object breaks the plane of the spell it no longer affects them. If you use it as a continous effect then it would IMO would act as a force that bleeds off the objets momentum. Where do the energy come from or go, well it depends on your game world mechanics. In my world magic energy comes from outside our normal physics and allows casters to break some of the laws of physics. So for your answer in my world the energy to be overcome comes from the "magic force" and any resistant forces goes back to the "magic force". I do not mean the Force as in Star Wars but magic that exzerts a force and can have a force exzerted upon it.
 So for example teleport is a big breaker of the laws of physics. In my game all the extra energy for a teleport just gets shunted to the "magic force" collumn and our physics is happy about it. A mage casts a fireball. No Problem the energy needed comes from the "magic force".

 I hope that helps but it may not.
MDC 

[FatSteve]

I use the "outside our universe" rule for magic energy too.  I also like the interpretation of increasing the coefficient of drag, but only in a specific direction. 

In the end, I will probably just consider it a "force" applied only in one direction.  The limitation of not being able to move objects will just have to be explained away with "magic" but that at least gives me a starting point for applying this to other situations.  (Perhaps the magic anchors on the target and draws the force to it from a pre-set direction.  This might explain why you can't move objects, and why it only works in one direction.)

But Force requires both mass and acceleration.  We could say the 1 pound of Staying I is the mass. (Okay you purists, the .454 kg of Staying I represents the mass.)  But what would be a reasonable acceleration?  This is where my ability to apply numbers to the real world starts to break down.   

I would like to assign a consistent rule for the "acceleration factor" of a Staying spell.  What would be a good factor?  A Staying I should be a relatively minor force, something a grown man could walk through with only a small effort.  A Staying True cast by a 30th level mage should be a huge force, something Conan the Barbarian would have trouble overcoming. 

Would an acceleration of 'X' feet per second per second, with 'X' being equal to the Staying number work?  This would make Staying X (roman numeral ten) exert a Force equal to 10 pounds, accelerated at 10 feet per second per second.  (Or 4.54 kg at 3m per second per second.)  That would keep the numbers simple, and still allow my players to be able to use the spell in interesting (but consistent!) ways.

And if that makes sense for the "normal" application of the spell, what would it do to that arrow?  It was just an example, but now that I brought it up, I'm curious.

FatSteve

[Dax]

Yes, the wording of that spell is a bit confusing.
But you have to hear it with the ear of an engineer (Stop, before you run around cutting ears).

The staying spell casts a force on the target. This force works on the exposed body area, therefore it is a pressure (a force that a giant could hardly recognized would blown away a gnom).
The weight unit were used to give a comparison; one pound of force nearly equals 10 times in Newton (yes, multiplied with the Earth Gravitational Constant (or whatever it ist called)).
(Every Morning you stand up against your body weight *10 as force  )

If you want to calculate the acceleration, you have to devided the applicated force [N] by the mass of the object.

In the above example (200 pound xbow, bolt, 100 ft) it seems that the bolt would reach the target but with a very low velocity.
If Staying isn't an 'U' type spell (read about 'U'type spells for attacking here: Link ), it might function; applicate the advantage for the caster as a distant modifier. The use of that spell (even if it is creativ) shouldn't be better than Deflection.
And remember at 100 ft the caster would have the problem to cast the spell on the hardly seen bolt.
With a Staying spell a caster could hinder the attacker to lift the crossbow on target - hinder (prevent if high level enough), a RR is always needed. Take the bolt with Telekinese gives the crossbow-man also a RR.

I heard the best example for a Staying spell from LordMiller:
A sword in a stone with a very high Staying cast on it, and only the true king would dispell it.
___

Sorry, it seems that my wording is as bad as the one of the spell. Feel free to ask if unclear.

[Winterknight]

As far as acceleration, I'd use the gravitational accleration, or an approximation that comes close for you (you aren't going to the moon after all.)  9.8 meters per second per second, or round up to 10 hexes per second per second.  Easier math. 

That interpretation could be applying the same force as gravity, in an altered direction, and limited to the pounds-force specified by the spell.

[FatSteve]

As far as acceleration, I'd use the gravitational accleration, or an approximation that comes close for you (you aren't going to the moon after all.)  9.8 meters per second per second, or round up to 10 hexes per second per second.  Easier math. 

I really like this idea.  It makes sense and is consistent.  Staying just simulates one pound of weight (or however many determined by the number of the spell) with the direction of gravity changed.  (And the condition that nothing can be moved by Staying alone.) 

And I don't mind really if this has a greater defensive effect in some situations than Defelections, because it has too many disadvantages that Deflections doesn't have (and the arrow thing was just for an example anyway).  Deflections is instantaneous, the arrow doesn't get a resistance roll, and if the arrow were fired from 10 feet away, Deflections would have the same effect - Staying wouldn't have enough time to slow it down. 

In fact, I applaud my players when they find creative uses for lower level spells.  I have always liked the "wise use of power" approach to playing a spell user. (Although when playing a spell user, I have to admit I like to fling fireballs with reckless abandon.  )

FatSteve

[markc]

 One thing to remember is that Staying I applies the force over a 10 second time frame and missile weapon attacks are applied almost instantly.

 The big question or problem I have is what are they going to do with the spell next game. So for example I am not so keen on the use of the spell to slow a run away wagon down or create a endless supply of energy by applying the force on one side of a wheel. IMO thoes appilcation go beyond the intention of the spell.
 IMO I think the spell came from the old D&D Bigbys Hand type of spells and were ment to grow in power from lower ranks to higher ranks. This is one of the problems we as gamers see today as opposed to the past. As we get older and our worlds become more complex we want answers for what is going on, I am the same. But sometimes thoes answers can come back to bit us because it is tough to think of every application of the spell we just ruled on.

MDC 

[FatSteve]

Well, unless they change one of the basic premises of the spell, it won't be able to turn a wheel, but I suppose it could be used to slow a runaway wagon at least a little (that wagon has a lot of mass, and even a staying X would only slow it gradually). 

I agree about generalizations biting me down the road.  And "down the road" is usually within a couple weeks with some of my players.  But I always hate to use the "well, because you just can't" answer as a GM.  The last time I had to resort to that was when an Arcanist used some of the spells from (I think) Spell Shaping and tried to change a Teleport to an Elemental spell and then cast a Teleport Storm on an army, sending them all several miles straight up.  I had to admit the spells as written allowed this, but c'mon.  (Eventually I backed off this ruling and allowed it - with the stipulation that the targets would get to choose their destination.) 

Good point about how fast missiles move.  Figure the missile leaves the crossbow at +- 300 fps.  The 1-pound from Staying is roughly double the mass of the bolt.  Staying applies an acceleration of roughly 2 Gs on the bolt, slowing it by 19.6m or roughly 43 feet per second per second.  Thinking of it that way, I think the Staying I would be too weak a force to do more than give the caster an additional DB, since the bolt would reach the caster in under half a second, even with the Staying.  Now, if a caster were to "waste" a much higher-level Staying spell, perhaps because that was all he had handy, then the bolt could almost literally drop at his feet as 200 Gs of acceleration were applied to slow it down.  (Acually a classic "cop nightmare":  I have to fire my gun to save myself and the bullets just kind of fall out of the barrel.) 

Cool.  Now I have a consistent answer for my power-gaming players. 

"Bigby's Grasping Hand!"  Now THAT is a memory from way back.  I think I last "cast" that spell sometime in the late 70's.  Or maybe it was the early 80's just before I started playing RM.  Either way, disco was still cool.  

FatSteve

[markc]

 I started gamign back in 79 and my introduction was a wizard in G1 or G2. I died very quickly but it was fun so I kepted on playing down through the years.

 The teleport thing does not work as I do not think you can change a spells type from utility. So as you said the people in the army would ahve to want to be teleprted. If you can use some good mind spells on them so they would rather be somewhere else then cast the teleprt the will go to where ever the spell takes them.

 Also IMO how you rule depends on your game IMO RM2/C/X tends to be a little more powerful IMO then RMSS/FRP. RMC has done a good job helping fix some of the problems so I would recomend getting the RMC Spell Law if you do not have it.

MDC

[markc]

 For the endless motion machine spell master the staying spell to move along a propeller like object and IMO it will move as long as the spell resets its self at the begining. Sort of like water under a water wheel or a current applied to a propeller shaft.

MDC

[FatSteve]

The teleport thing does not work as I do not think you can change a spells type from utility.

I read through the spell again, just out of curiosity, and also because that player will likely try to do something similar in the future and it is best to be prepared.  The 20th level spell Spell Typing from the Arcanist Base list Spell Shaping allows the caster to change the type of any spell to any other type of spell, except for Information.  One example the text gives is to make a Sleep spell into an Elemental spell, thus preventing any resistance roll.  It does not mention Utility spells at all. 

I remember when he originally came up with the idea for the Teleport Storm.  I could not find a rule that said he could not do that.  Since I hate to use the "Because I said so" reason as a GM, I have instituted a policy of killing off all Arcanists before they reach 20th level... 

I started playing around christmas of '77.  My older brother got that ancient boxed set of D&D, and I played a cleric who ran around bashing people with a mace.  It might even have been G1 and G2, but my memory is starting to go so I can't be sure.  I like to think my gaming got more sophisticated after a few years...

FatSteve

[markc]

 I did look up the spell in RMSS:AC pg 72 and it says at the bottom it changes they way that spells are saved against. I allways remind my players that if tehy can do it then the NPC's can do it. This solves a lot of problems and tends to make most of them happy.

 I am fully on board with creative spell use and IMO pure's and Arcane professions would IMO push the envilope in my eyes. [That is I envision them being more able to craft new spells and then allow them to be learned by other mages, Its not that any of the 3 realms purs cannot do this it is just easier for the arc's. But that is my game and your is probably different as I do not think any 2 RM games are the same]

MDC

 

[FatSteve]

But that is my game and your is probably different as I do not think any 2 RM games are the same

I agree.  That is one of the things that keeps me gaming.  No two games are the same.  My last campaign used some seriously-different magic rules that a lot of people would really not like. ("Strange Magic" may possibly appear in a Guild Companion near you.)  The game was a lot of fun, and ran almost every week for 22 months.

My next game (coming soon to a gaming table near me) will use pretty "standard" magic, but I'm adding a lot of elements from "At Rapier's Point."  Kind of a Three Musketeers with magic being fairly common.  I have no idea where it is going to go...

FatSteve

[Marc R]

I think this idea would work well actually. .

If you cast Staying I on a 1# rock and chose up as the direction, it would float. (Technically, if it were exactly 1 pound, air pressure would cause it to "float" to the top of the atmosphere. Actually any object who's specific gravity was lowered beyond that of air would float up that way. . .the spell cannot move anything, but if you did that, the force of air pressure would cause it to float off, just like it makes a helium baloon float away.)

In RMC, 20 arrows weigh 3 pounds, or .15# per arrow. . .casting staying, and choosing down would be the same as tying a 1 pound weight to the arrow, and it would plummet to the ground way short. any lateral direction would send it way off course, up would send it into space per the above. . .same would be true for a 1/2 pound bolt. . .it would shoot, just nowhere near where the archer aimed it.

Likely, the object so stay/floated would actually just soar up, then drop when it ran out of duration, not actually make it out of atmosphere.

It's an F spell though, so the arrow in archers hand/bow/x-bow would get a RR as the archer. . .so it's not quite aim untrue.

That does seem to violate the spirit of the name of the spell "staying" and the "won't move objct on it's own". . . .

How about this counter oddity. . .what if you got your arbelast out. . .mounted a 1.01# bolt in it. . .cast staying I on it and called the direction "Up". . . . .I wonder how far you could shoot it with no gravitational drag, just air drag?

[FatSteve]

That is exactly the sort of thing my players would come up with, and is right along the lines of what I was thinking.  I have always thought there were too many forces in play, even with something as simple as a crossbow bolt flying at a target, to allow for changing one of them without significant consequences. 

Now I can just imagine one of my players coming up with this and me saying, "well, treat it like a one pound object resting on the target, with gravity in the direction specified by the spell."  The HP calculators would fly from their quick-draw holsters, and let no one get in the way of the math...

[twh]

The HP calculators would fly from their quick-draw holsters, and let no one get in the way of the math...

RPN rocks!

That doesn't make me a nerd, does it?