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EarFall
2009-05-26, 10:16 AM
Question, has anyone ever had a problem with momentum? For example, if someone puts caltrops in the square you are charging into as you are charging, can you stop on a dime? Can your horse? Do you run into the readied prismatic wall? This is 3.5, but it applies to 3.0 and 4e as well (1e and 2e would obviously say momentum exists, and thus the person is screwed).

Tiki Snakes
2009-05-26, 10:24 AM
Question, has anyone ever had a problem with momentum? For example, if someone puts caltrops in the square you are charging into as you are charging, can you stop on a dime? Can your horse? Do you run into the readied prismatic wall? This is 3.5, but it applies to 3.0 and 4e as well (1e and 2e would obviously say momentum exists, and thus the person is screwed).

This is what the piece of fleshy aparatus behind the screen is used for. It's called a 'Dungeon Master' and is quite handy in adjudicating such things, for example, by calling for a check to see if you can, infact, stop in time, or letting you know otherwise.

I hear they are really catching on. ;)

shadzar
2009-05-26, 10:24 AM
All editions have sort of a "slowed" condition. Caltrops would effect things if not stop them completely.

You would probably be best to think of it like a trap. Most times a DEX check would tell you if you falter or stumble or keep moving, but the damage sustained and continuing effects of not removing sharp implements from your feet should bring you to a halt at least long enough to remove them.

Thus ending your forward momentum.

Volkov
2009-05-26, 10:27 AM
If they really want to screw you over, they could haste you. Thus you have less time to react to stop yourself from impaling yourself on the caltrop.

EarFall
2009-05-26, 10:29 AM
This is what the piece of fleshy aparatus behind the screen is used for. It's called a 'Dungeon Master' and is quite handy in adjudicating such things, for example, by calling for a check to see if you can, infact, stop in time, or letting you know otherwise.

I hear they are really catching on. ;)

LOL I understand that. I guess the part that makes it hella cheesy is prismatic wall.... who wouldn't want to ready an action against the charger?

derfenrirwolv
2009-05-26, 10:47 AM
Grease spell references it briefly... how fast a creature is going when it hits the grease can affect the reflex save.

That spell gets REALLY fun when used as a held action against a charging foe...

Keld Denar
2009-05-26, 10:52 AM
Grease spell references it briefly... how fast a creature is going when it hits the grease can affect the reflex save.

That spell gets REALLY fun when used as a held action against a charging foe...

Or as an Initiate of the 7fold Veils...Immediate Duel Warding. Suck my Indigo and Violet!

Mastikator
2009-05-26, 11:10 AM
Does D&D at large even bring up acceleration when you run or stop? If it doesn't then just go with the laws of physics, I guess you could perhaps say that the round that you use to start/stop running you only reach half as long, and therefore if you charge and stop you must at least move half of your total length per round.

A character with 30 ft per round running at x4 speed runs 60 feet, then 120, and to stop takes another extra 60. Unless there's something stopping him, like a spiked wall. Then you'll have to calculate what length you'd have to fall to reach his velocity and count it as falling damage.

I'd love to cough up all the forumulas but I've got to go. I'm sure someone else can do the math.

Piedmon_Sama
2009-05-26, 11:11 AM
One of my personal peeves with D&D combat is that people can't get "knocked back" out of their square unless you're doing something like using a Bull Rush or Monstrous Blow or whatever it's called.... or that being smacked by a broadsword never threatens to knock someone prone. I've considered houseruling this for a long time but I was never able to think of something that didn't make things outrageously imbalanced in favor of powerhouse fighters.

Eldariel
2009-05-26, 11:19 AM
One of my personal peeves with D&D combat is that people can't get "knocked back" out of their square unless you're doing something like using a Bull Rush or Monstrous Blow or whatever it's called.... or that being smacked by a broadsword never threatens to knock someone prone. I've considered houseruling this for a long time but I was never able to think of something that didn't make things outrageously imbalanced in favor of powerhouse fighters.

Use Alternative Critical Tables along with Fumble Tables. Those always make life more interesting and enable adding elements that are normally absent in D&D combat (like losing limbs/getting limbs damaged, losing footing and falling prone, getting knocked backwards, etc.).

Heliomance
2009-05-26, 11:27 AM
No! No momentum! There are three words which should tell you just why adding momentum to D&D is a horrendously bad idea: Commoner. Rail. Gun.

EarFall
2009-05-26, 11:32 AM
No! No momentum! There are three words which should tell you just why adding momentum to D&D is a horrendously bad idea: Commoner. Rail. Gun.

The problem is that's unrealistic, even if it obeys the laws of physics. What alignment would do that? Only CE, and even most of them wouldn't think of doing that. It's just something that won't come up unless a player or DM metagames horribly. But someone WOULD try setting up caltrops as someone is running by, because that's what people do. People don't try to throw commoners at people as a normal tactic.

shadzar
2009-05-26, 11:36 AM
The problem is that's unrealistic, even if it obeys the laws of physics. What alignment would do that? Only CE, and even most of them wouldn't think of doing that. It's just something that won't come up unless a player or DM metagames horribly. But someone WOULD try setting up caltrops as someone is running by, because that's what people do. People don't try to throw commoners at people as a normal tactic.

Hold on there! I had a true neutral character that thought a villager catapult to be the best way for evensided fight.

The villager risks death while chances killing an enemy. That's balance. If you can fire wizards it is even better because they can cast something prior to becoming the ammunition themselves. :smallsmile:

EarFall
2009-05-26, 11:39 AM
I don't want to get into an alignment debate... and the commoner rail gun isn't a mundane use of the laws of physics, it's trying to applying a lot of factors to a very, very specific instance. I'm asking if you throw something to stop a charging opponent, or make them get hurt.

Edit: and that's not balance, because if the commoner misses, he still dies.

Eldariel
2009-05-26, 11:41 AM
Commoner railgun is a great idea except for the "only so many free actions can be taken in a round"-part. That is, it works as long as there's nobody adjudicating the rules. Therefore it's a great joke.

shadzar
2009-05-26, 11:44 AM
I don't want to get into an alignment debate... and the commoner rail gun isn't a mundane use of the laws of physics, it's trying to applying a lot of factors to a very, very specific instance. I'm asking if you throw something to stop a charging opponent, or make them get hurt.

Edit: and that's not balance, because if the commoner misses, he still dies.

But if he hits he arrests the momentum right?

I surely hope people don't leave Newtonian physics out of their games. :smalleek:

I mostly like to throw barrels and such at people following me. They fall, momentum ceased.

Heliomance
2009-05-26, 11:45 AM
The problem is that's unrealistic, even if it obeys the laws of physics. What alignment would do that? Only CE, and even most of them wouldn't think of doing that. It's just something that won't come up unless a player or DM metagames horribly. But someone WOULD try setting up caltrops as someone is running by, because that's what people do. People don't try to throw commoners at people as a normal tactic.

I don't believe you understand the concept of the Commoner Rail Gun. Allow me to explain.

You obtain an arbitrary number of commoners, and get them all to stand in a line. You then tell them all to ready an action to pass a quarterstaff to the next person in the line on receiving it. You then hand a quarterstaff to the first commoner. His readied action triggers, and he passes it to the next commoner as a free action, triggering his readied action, and so on. The quarterstaff passes all th way down the arbitrarily long line as a free action, thus attaining a near-infinite velocity. If you then apply physics to this, work out just how fast it's going and thus how much momentum and kinetic energy it has, the damage at the other end when the last commoner lets go is obscene. If, on the other hand, you accept that physics has no place in D&D, it does 1d6 plus strength damage with a -4 proficiency penalty on the attack roll, and a further -4 for throwing a weapon not designed for the purpose.

EarFall
2009-05-26, 11:55 AM
I don't believe you understand the concept of the Commoner Rail Gun. Allow me to explain.

You obtain an arbitrary number of commoners, and get them all to stand in a line. You then tell them all to ready an action to pass a quarterstaff to the next person in the line on receiving it. You then hand a quarterstaff to the first commoner. His readied action triggers, and he passes it to the next commoner as a free action, triggering his readied action, and so on. The quarterstaff passes all th way down the arbitrarily long line as a free action, thus attaining a near-infinite velocity. If you then apply physics to this, work out just how fast it's going and thus how much momentum and kinetic energy it has, the damage at the other end when the last commoner lets go is obscene. If, on the other hand, you accept that physics has no place in D&D, it does 1d6 plus strength damage with a -4 proficiency penalty on the attack roll, and a further -4 for throwing a weapon not designed for the purpose.

Ah, well in that case, I'm asking if momentum as it REALLY WORKS has a place in the game, where as that, I see, has nothing like real physics in it, just a game mechanic being silly.

Edit: Although it was funny to tell the DM I could move 2,000 feet, to the front of the army, by mounting and dismounting horses, it's much in the same vein as that joke.

TheDarkOne
2009-05-26, 12:34 PM
Characters don't have to stop on a dime to come to a stop with in one square, they have 5 feet to stop in. This is an extremely reasonable amount of room to stop in for most people taking a double move, and even characters taking a run action probably wouldn't find that much trouble stopping in 5 feet of space. Really, people accelerate and stop quite well due to the nature of how we move about. I don't think the game would benefit from adding rules specifically to deal with things like this except for some extreme cases(ex a running 20th level monk with the run feat, who has been polymorphed into an elephant), which the DM should be able to deal with fairly easily if and when they come up.

EarFall
2009-05-26, 12:45 PM
Characters don't have to stop on a dime to come to a stop with in one square, they have 5 feet to stop in. This is an extremely reasonable amount of room to stop in for most people taking a double move, and even characters taking a run action probably wouldn't find that much trouble stopping in 5 feet of space. Really, people accelerate and stop quite well due to the nature of how we move about. I don't think the game would benefit from adding rules specifically to deal with things like this except for some extreme cases(ex a running 20th level monk with the run feat, who has been polymorphed into an elephant), which the DM should be able to deal with fairly easily if and when they come up.

Actually, people in D&D (3.5) run ridiculously fast, especially for a combat situation.

Quietus
2009-05-26, 12:51 PM
In general, if they want to stop, they can stop. I might adjucate a reflex save to stop in time, though - in the case of the prismatic wall, the save is at the wall's DC. For caltrops, I'd have them roll and hope they roll high enough or low enough that I don't need to come up with a specific number.

EarFall
2009-05-26, 12:54 PM
In general, if they want to stop, they can stop. I might adjucate a reflex save to stop in time, though - in the case of the prismatic wall, the save is at the wall's DC. For caltrops, I'd have them roll and hope they roll high enough or low enough that I don't need to come up with a specific number.

I definitely know what you mean on the last one. Half the rolls I ask players to make that don't have a rule I'm like "throw a 5 or below or a 15 or above, please..."

TomKatt
2009-05-26, 01:03 PM
As a dm in that situation i would probably have them roll a spot check 5 to 10 feet from the cal trops to see if they even see them dc dependent on the circumstances and then a refelx save to see if they can stop in time... its as simple as that no need to add in physics, just use the rules provided and every thing goes smoothly.
No worries about calculating velocity and adding in factors like friction and inclines and blah blah blah....:smalltongue:

Quietus
2009-05-26, 01:16 PM
I definitely know what you mean on the last one. Half the rolls I ask players to make that don't have a rule I'm like "throw a 5 or below or a 15 or above, please..."

The worst is when they roll a ten... and add three. Then you get to mentally go "CRAP! Is the DC 10 or 15?"

valadil
2009-05-26, 01:20 PM
D&D does not model physics very well. It's up to your GM to apply physics to the game and up to you to listen to him. I once pissed off some players by ruling that the knight jumping into a rowboat would displace the rowboat upon impact. They didn't like entities moving when it wasn't their turn.

That said, I'm not knocking D&D. At some point you have to cut out the real world and just go with an easy to use approximation. GURPs has rules for momentum. If you move in a straight line, you can run the next turn at +1 to your run speed. I forget where it caps (probably something like 150% total speed) but the idea is that you gain momentum and pick up speed as you run. This is simple in and of itself, but having several dozen rules like this really slows the game down. Personally, I prefer a fun game over an accurate simulation.

Volkov
2009-05-26, 01:21 PM
No! No momentum! There are three words which should tell you just why adding momentum to D&D is a horrendously bad idea: Commoner. Rail. Gun.

What is a Commoner rail gun. I've heard of it, but I've never seen it done, probably so my APL 107 party doesn't use it. I'm having enough trouble creating original monsters to fight them, mainly because it's hard to optimize the skill sets.

Heliomance
2009-05-26, 01:55 PM
Already explained above.

Lord Herman
2009-05-26, 02:26 PM
This thread explains all you need to know about momentum in D&D. And about destroying the world with a pig.

Epinephrine
2009-05-26, 02:36 PM
I've been tempted to add some momentum rules to D&D; at one point my character was running at an enemy (well, double move, not a full run) and ended ~25' back. Someone casts an entangle on their turn, covering the area beween enemy and I. On my next turn I wish to jump it; I moved last turn in a straight line toward it, should I count as having a running start even though I only have 5' of move before my jump?

I'd say yes, and the DM agreed. But by RAW, I don't think so. Momentum makes some sense, but I think it comes down to a lot of DM rulings.

Curmudgeon
2009-05-26, 03:16 PM
Keep it simple. Ignore momentum. The D&D movement rules are based on assuming movement at a hustle, which is half run and half walk. Experienced adventurers are going to be going faster when they see clear ground ahead, and slow down when they see obstacles or can't see. So they'll be moving at a walk when coming up on something like caltrops, and can easily stop without continuing into known obstacles. A 5' square's a whole lot easier to stop on than a dime, and even while charging you're going much slower than running speed.

Just keep it simple.

Devils_Advocate
2009-05-26, 03:30 PM
Notably, momentum is not conserved in D&D, because thanks to magic, an object's mass isn't a constant.

Magically enlarge an object. Does it maintain its momentum or its velocity? Lots of people seem to assume that the correct answer is "Momentum." But the thing is, it can only maintain its momentum in one inertial reference frame! The change in velocity will cause its momentum to change in other reference frames. In fact, its velocity needs to remain constant in order for it to maintain its momentum in the reference frame matching its velocity.

So I say that's what happens. Its velocity remains the same. Which means that, yes, you can get stupidly large things moving unusually fast by shrinking them, throwing them, and then enlarging them. Yes, you're creating energy from nowhere. You can do that when you can create mass from nowhere. Magic is plainly violating the laws of physics here.

Incidentally, magical enlargement seems to slow living creatures, but not nonliving mechanisms, relative to their size. See, if you're magically enlarged, your speed stays the same (as OoTS notes), and thrown weapons deal their normal damage despite being thrown by your enlarged body, which you'd think would push them through twice the space in the same time and thus get them moving twice as fast. However, projectiles deal damage based on the size of the weapon that fired them. (Both thrown weapons and projectiles return to their normal size upon leaving your possession.)

And that's why Enlarge Person gives -2 Dex; you've been slowed down, relatively speaking. You're moving in slow motion, but at the same absolute speed as you were earlier, because you're bigger.