GM and PC disagree on levitate, a little help?

[mevans7]

Basically, I've got a character in the group who is very weak physically, with a Str of 4. She's a witch, and it doesn't adversely effect her ability to contribute to the group because all she's ever really got that I'd bother to count is her robes, a small dagger, PomPom (her familiar) and various scrolls that don't contribute to weight. Now, she wants to use levitate to move things around, mostly levitating them, being able to fly herself, and "dragging" heavy objects at half speed, or 30ft/round.

Now, my interpretation of what she wanted to do, and I thought that I was being generous, was that she could pull no more than 400lbs this way, citing the rules regarding pulling objects along the ground. I considered levitation as being equal to pulling something on wheels or over ice, or 10x her heavy load weight of 40lbs, even though at level 6 she would be able to levitate a 600lb object. I rationalize the object may be weightless, but it still has mass. She could still levitate objects up to the allowed maximum based on her level, but she'd need help to move them.

I'm honestly not really comfortable letting her move something that quickly. I'm no physics major, but accelerating a 400lb boulder over 5ft/sec would require a bit more force than a person with 4str could muster, IMO, but I'm really not sure how else to adjudicate this.

[VoxRationis]

Well, I'm not sure about your exact numbers, not having the tables in front of me, but your basic idea is sound: the amount she can pull is limited by her strength. Personally, I would rule that you would get a more favorable multiplier for something levitated than something on ice, since the friction with the air beneath the object is negligible compared with that it would apply to ice.

[nedz]

Bear in mind that 3.5 doesn't do momentum so real world physics is moot.

Lifting and Dragging

A character can lift as much as his or her maximum load over his or her head.

A character can lift as much as double his or her maximum load off the ground, but he or she can only stagger around with it. While overloaded in this way, the character loses any Dexterity bonus to AC and can move only 5 feet per round (as a full-round action).

A character can generally push or drag along the ground as much as five times his or her maximum load. Favorable conditions can double these numbers, and bad circumstances can reduce them to one-half or less.
Levitation would seem to be a favourable condition allowing a ten times maximum load.
You could extend the above to allow 5' moves for twenty times, but that would be a house rule.

[holywhippet]

It seems to me you can't treat your possession and what you are pushing separately. If the items you are carrying weight 10 pounds for example you'd only have 30 pounds worth of carrying capacity so you could only pull 300 pounds along. The rules don't say that explicitly from what I can see though.

[Spore]

I'm honestly not really comfortable letting her move something that quickly. I'm no physics major, but accelerating a 400lb boulder over 5ft/sec would require a bit more force than a person with 4str could muster, IMO, but I'm really not sure how else to adjudicate this.

You'd be surprised what is possible when you have the load on wheels with almost no friction. Talk about a palette of beer sixpacks easily weighing 800 pounds. Using a manual fork lift (idk ne english word) makes this weight easily pullable on even ground.

[VoxRationis]

You'd be surprised what is possible when you have the load on wheels with almost no friction. Talk about a palette of beer sixpacks easily weighing 800 pounds. Using a manual fork lift (idk ne english word) makes this weight easily pullable on even ground.

The term, I believe, is "hand truck," or sometimes "hand cart," and part of its ability is due to leverage, but you make a good point.

[NoACWarrior]

Ok so from what I read from levitate the spell is that it does not negate the amount of effort required to push or drag an object - but offers a friction-less and thus favorable method for pushing or dragging.
Normal heavy load for a Str 4 character is 40 lbs, with pushing or dragging limit being 200 lbs, and favorable conditions making it 400 lbs total limit with a levitating object.

According to SkipW in all about movement part 2, you move at 1/2 your speed if you are using the dragging rule to move something that exceeds your max load.

[Anachronity]

From a physics perspective, she should be able to move almost any amount of weight provided she can levitate it, for as long as she can levitate it. The only thing stopping her from doing so would be air resistance, which is based on velocity and is negligible in a situation where speed is on the scale of 30 feet per round. However, once she began moving the weight it would be very difficult for her to stop it again because doing so would require the same amount of effort in the opposite direction (although she could always just dismiss the spell).

The issue is that acceleration and momentum do not exist in D&D. I would say that it takes a full round of pushing to accelerate the load to 5 feet per round for her, after which point the weight moves in a straight line independently of her. From there, she could take a 5-foot step and accelerate it again to 10 feet per round, but after that she wouldn't be able to keep up with it while still applying meaningful force. Similarly it should take a full round to decelerate it by 5 feet per round.

[holywhippet]

From a physics perspective, she should be able to move almost any amount of weight provided she can levitate it, for as long as she can levitate it. The only thing stopping her from doing so would be air resistance, which is based on velocity and is negligible in a situation where speed is on the scale of 30 feet per round. However, once she began moving the weight it would be very difficult for her to stop it again because doing so would require the same amount of effort in the opposite direction (although she could always just dismiss the spell).


I disagree, you aren't taking inertia into account. Consider one of those super fast trains like in Japan where the whole train is suspended in the air via electromagnetism. Effectively speaking it is levitating, but you aren't going to just be able to start pushing one along. The physics law applicable is F = ma (force = mass X acceleration). Consider how much force a person could generate then divide that by the mass of the train. Acceleration will be so tiny as to be negligible.

[firebrandtoluc]

Physics doesn't apply in D&D. Otherwise your character's constant force would result in linear acceleration and therefore exponential velocity increase. You would need to account for air resistance, but even a 4 strength can push hard enough to get it going at a good clip. If physics applied anyway... since it doesn't... use the rules. Those are the dungeon physics.

[Knaight]

I'm honestly not really comfortable letting her move something that quickly. I'm no physics major, but accelerating a 400lb boulder over 5ft/sec would require a bit more force than a person with 4str could muster, IMO, but I'm really not sure how else to adjudicate this.
I'm also no physics major, but this is fortunately pretty simple physics. Math below:

Lets say that we're looking at 30 feet per round here. Assume it starts immobile, and 6 seconds later is at maximum velocity. With constant acceleration, said maximum velocity is 60 feet per round, or 10 feet per second. This is achieved over 6 seconds, which works out to 1.67 feet per second per second, or 0.509 meters per second. The boulder is 181 kg, so the forces exerted involve a whopping 92 N.

92 N is nothing. To put it in context - in order to jump, you have to exert more force while jumping than gravity exerts on you. So, lets take a 70 kg person, which is about average. It takes over 686 N to jump at all. Or, lets take holding things. The character can lift 40 pounds above their head. That's 178 N right there, and that's just to hold it against gravity. Actually moving the object takes more than that. Assume that it takes a standard action to do the lift, call it 3 seconds. Let's also assume the character is short, and have it only be a 2 meter lift total (I'm assuming partially outstretched arms here). I'll assume that it starts at motion, and let deceleration be instantaneous, along with having 100% efficiency in the movement. At 2 meters over 3 seconds, a final speed (prior to immediate deceleration) is 4 meters per second, which works out to an acceleration of 4/3 meters per second. This adds another 24.2 newtons to the constant holding. So, 202 N.

So the question is, is it reasonable for someone to exert less than half half as much pushing force as they can exert lifting force? I'd have to go with a yes here. It's reasonable for people to exert far more than that, particularly as the just holding the object above the head involves 178 N exerted largely with arm muscles, and the pushing is going to be more with legs.

The short version: It takes over twice as much force for the character to lift the weight above their head that they can lift, which is harder force to exert. Moving the 400 pounds is totally fine at the speeds involved. A dead run isn't happening by D&D rules, though there's no actual reason it shouldn't be achievable realistically, provided that turning isn't really happening.

[jedipotter]

Note you can't ''Fly'' with the spell levitate. You could float up and grab something, like a ceiling and pull yourself along. But you can't fly.

And to push or drag an object does not sound so great to me. Mage hand would be much more useful. As an unseen servant. Or a summoned creature.

[NoACWarrior]

Note you can't ''Fly'' with the spell levitate. You could float up and grab something, like a ceiling and pull yourself along. But you can't fly.

And to push or drag an object does not sound so great to me. Mage hand would be much more useful. As an unseen servant. Or a summoned creature.

Thats not whats happening. Whats happening is Levitate is cast on a load - say a bunch of saddle bags, and the character in question is flying while pushing or pulling the saddle bags.

[Mnemnosyne]

Levitate doesn't make things weightless, it lifts things up and down. Any lateral movement is exactly as difficult as it was before, whether it's being done under the power of the levitated or whether an external force is pushing it. You'll note that levitate gives no penalties to bull-rushing, for one; the levitating creature is not automatically pushed along if he doesn't want to be. Additionally, if levitate made a creature or object behave as if it were in freefall (aka, 'zero gravity'), then it would require a complex set of rules for when you push off of something and keep moving, etc. It does not. Therefore, levitate should have almost no effect whatsoever on someone's ability to push/pull/drag an object.

Frankly though, your player is going about things really poorly and trying to use the wrong spell for the task. Tenser's floating disk is a 1st level, hour/level spell that can carry 100 pounds/level of load atop itself and moves at the caster's normal speed 3 feet above the ground. Greater floating disk is a 4th level spell that works like the first, but can also fly at 20 ft. perfect maneuverability. She should be using those spells to transport heavy objects, because that's exactly what they're designed for, and they're vastly more effective than levitate. Levitate might be needed to lift a heavy object three feet so it can be placed on the disk, but it's definitely not a good spell to use to try to move the object directly, especially due to its minute/level duration.

[Anachronity]

I disagree, you aren't taking inertia into account. Consider one of those super fast trains like in Japan where the whole train is suspended in the air via electromagnetism. Effectively speaking it is levitating, but you aren't going to just be able to start pushing one along. The physics law applicable is F = ma (force = mass X acceleration). Consider how much force a person could generate then divide that by the mass of the train. Acceleration will be so tiny as to be negligible.

Inertia is the property of moving objects to continue moving and stationary object to remain stationary, until acted on by a force (i.e. someone pushing on it). Naturally there is a practical limit to how fast she could move an object if it is very massive (such as the train), and for such a massive object you would increase the amount of time needed to push it before it began moving (in D&D) or the amount of time you would need to push it before it began noticeably moving (in real life). But even for something as large as a train this would still be possible.

Consider that a character with 4 strength can lift 80 pounds over her head. This means that she can apply enough force to accelerate 80 pounds by 9.8 m/s^2, or about 32.3 feet per second^2 (since she must counteract gravity). The levitation cancels out gravity, but she is still free to apply that same force to the now-weightless object. For a 600-pound object, she can generate (32.3/7.5)=4.3 feet per second^2. Since a round is 6 seconds, she could conceivably accelerate the object by 25.6 feet/second, or about 4.25 feet per round. This is assuming she is able to apply the same leverage to an object that is beside her as she can to an object she is holding above her head, which isn't too farfetched. All the same, I would maybe increase it to two full rounds of pushing to get the box floating at 5 feet per round.

After a point it becomes difficult to keep up with the object while still applying that same force, which is why I suggested limiting it to 10 feet. Realistically, it would actually be quite a bit higher than that. If you could somehow keep up with the object then you could indeed keep accelerating it forever.

I would agree that physics can be dangerous in D&D, but in this case I think it's not unreasonable to apply. It could make the next random encounter quite a bit more interesting if she had to worry about her luggage getting away. There's really no reason not to treat it this way when the rules are a little unclear about it (strictly speaking even ice isn't as frictionless as levitation).

EDIT: Actually Mnemnosyne makes a pretty good point.

[HunterOfJello]

Pushing an object that has levitate on it should be very easy. Stopping it after you've accelerated quite a bit would not be.

A character with 4 strength would be restricted to the speed she could carry it at and would have to take extra action to stop it from moving (if she even can stop it any longer).

[mevans7]

All good points, and theres a few I'd like to address specifically:

One reason I avoided using physics directly, and thanks Knaight for those calculations, is because its exactly that sort of thing that allows the "peasant railgun" to exist.

Mnemnosyne makes some great points, that are more reliant on the rules as written, and I could bring up the existence of the . Now I don't generally like telling my players they can't do something that I think is creative and/or inventive. However, I'm pretty sure the reason she wants to use levitate this way (and not the Disks) is to basically drop boulder bombs on things, which is neither creative nor particularly fun for anyone but her. Obviously using levitate to drop something on an enemy is fine, but I'd rather her have to coordinate with the group to set up the trap, and not just be able to move the boulder as she see's fit.

[ericgrau]

Assuming you use physics where reasonable and not covered by rules, which the DMG does say to do, here's a simplification:
She may travel with almost any load limited only by width and height. If it is too wide and high then it becomes like a sail and may slow her down a great deal. I'd say 4'x4' or an equal area is a good limit before you start imposing penalties. Especially with her low strength. In high winds the limit may be lower than that. IMO at 4'x4' impose a -2 penalty to the strength check (the DMG suggests -2 as a general purpose penalty), and for other areas adjust accordingly. Probably another -2 for every doubling in area (or -4 if both width and height double to 8'x8').

As soon as combat begins she should be able to spend a move action to stop up to 5 times her light load*. For each additional 5 times her light load she must spend another move action to fully stop it, otherwise she only partly stops it. Otherwise the load drifts forward like a runaway carriage, with or without her. Her light load is 13 lbs. So let's say she wants to carry around 390 lbs (30 times her light load). If she spends a move action in round 1 to slow it down it moves forward 25 feet instead of 30 feet. Then the next round she does the same and it moves forward 20 feet. The next round she blows 2 move actions and it only drifts forward 10 feet. Getting it moving again takes the same amount of time. Air resistance is negligible for most purposes at walking speeds.

*FWIW I used F=ma, a = g at m = light load, v=at, and 3 seconds per move action.

[Captnq]

It moves when she pushes. It stops dead when she lets go. Levitate only affects one object, so it would only affect one scroll. It is not weightless. 0 weight. Put any weight on it, it falls to the floor. Get a basket, make ti float. Climb in and watch it fall. Why? Only affects one object.

Tenser's floating disk and a metamagic extend rod, maybe a pearl of power 1st level. Cast it at 4th level. Have her carry around a Light balista. It's 5'x5' and weighs 400 lbs. 3d8 damage should bring her combat effectiveness back up to par with the party.

[Mnemnosyne]

Mnemnosyne makes some great points, that are more reliant on the rules as written, and I could bring up the existence of the . Now I don't generally like telling my players they can't do something that I think is creative and/or inventive. However, I'm pretty sure the reason she wants to use levitate this way (and not the Disks) is to basically drop boulder bombs on things, which is neither creative nor particularly fun for anyone but her. Obviously using levitate to drop something on an enemy is fine, but I'd rather her have to coordinate with the group to set up the trap, and not just be able to move the boulder as she see's fit.
This is actually possible with greater floating disk quite easily. Place a heavy object upon the disk, and since it has a fly speed, fly up above the target with the disk, then dispel the disk. I am not sure if there are rules about how this would work, though; does it require an attack roll? Allow a reflex save to avoid? I seem to remember someone mentioning there are rules about it, but I cannot find those rules right now.

However, damage would be considerably less than she's probably imagining, whether she uses levitate or greater floating disk to achieve the effect. A falling object deals 1d6 damage for every 200 pounds of weight if it falls 10 feet, so a 600 pound object would deal 3d6 damage if dropped from 10 feet above the target. Each 10 feet above that adds 1d6 damage, but then we get into the question of targeting. If we drop a 600 pound object from 180 feet in the air, it will do 20d6 damage (the maximum) to whatever it hits, but I don't know if there exist rules for hitting a target with a dropped object. At best I would say it is a ranged attack roll with a range increment of 10 feet, so every 10 feet above the target beyond the first 10 feet gives another -2 to hit...meaning this attack roll has a penalty of -34 to hit. Which frankly makes a good deal of sense; I've tried to drop objects to hit a target from heights as little as 10-15 feet, and it is very difficult once you get a decent distance above the target. A big object 15-20 feet, sure, but a big object 180 feet is like a small object 15-20 feet, and it becomes difficult again.

[Leviting]

can't you just stand on a large tome or something and ride around on that, while it is levitating along? That would certainly allow you to "fly"

[TuggyNE]

On the physics side of things, note that a normal human with average strength (and thus a 500 lb drag limit) can push a multi-ton car; acceleration is very slow, but it can be done. So it should probably be possible to have exceedingly favorable circumstances (i.e., modern bearing designs) that do more than merely double the drag limit.

Not that levitate is really the preferred means of accomplishing this, but, y'know, the principle of the thing.

[mevans7]

Mnemnosyne she's probably going to try to drop it on something more stationary, but I see what you're saying. From that distance, even hitting something with a DC5 becomes a matter of chance, and it should be.

I think I'll give her half her fly speed, as stated in the Fly spell description for carrying a medium or heavy load, and limit the amount she can move to 400lbs, considering that levitating would give the the best conditions to move things as per the carrying capacity rules.

Thanks for helping me sort this out.