D&D 5E Wall of Force and spells

[greg kaye]

The Wall of Force is a field effect that absorbs energy, not a solid object. When something hits it, it's kinetic energy is absorbed, so it simply stops dead. It is not cut or damaged in any way.

That's not in the spell's description:

Things hitting the wall certainly stop dead, but I'd think that this is because they hit a wall.

 

[greg kaye]

It’s a good idea, though, as a way out of Wall of Force suddenly becoming the dragon dicing spell. Otherwise…any mathematicians want to calculate the impact of a ten ton dragon onto a (let’s go metric) 7mm, absolutely immovable edge at, say, 50kmph? That would be a hell of a lot worse than falling damage. I think we’d have two half dragons.

I don't see that mathematics in 5e would have to work to that extent.
A mammoth (with lots of hp) and a squirrel (with 1 hp) both falling 50 feet would both sustain 5d6 damage - but, in reality, the squirrel might survive while the mammoth would splat.
A dragon at dash speed is only moving a bit faster than the speed that a real-world object moves after falling 10 ft.

 

[Oofta]

I don't see that mathematics in 5e would have to work to that extent.
A mammoth (with lots of hp) and a squirrel (with 1 hp) both falling 50 feet would both sustain 5d6 damage - but, in reality, the squirrel might survive while the mammoth would splat.
A dragon at dash speed is only moving a bit faster than the speed that a real-world object moves after falling 10 ft.

The problem for the mammoth vs squirrel is that the rules we have are only for humanoids falling, and I'd say medium humanoids at that. In a vacuum the mammoth and squirrel are both going to suffocate quickly while also falling at the same speed. The terminal velocity of a mammoth is significantly higher than that of a squirrel*, kind of like comparing a falling bowling ball to a feather. In addition, in the real world unlike D&D, truly massive creatures have to deal with the reality of mass and the strength of bones. A giant would collapse under their own weight in the real world.

In any case when in combat (which is all we have for dragon flight speed) you really aren't moving all that fast, the flight speed is 80 feet per round base. So about 30% faster than the speed of a person moving and dashing; it would hurt to run into a wall that fast but likely wouldn't be deadly. Because it's D&D, the mass of the creature doesn't really matter much.

So how fast are you going if you fall 10 feet? Well, according to Omnicalculator (I really wanted to use the Splat Calculator for this, but my brain hurts converting to metric) after falling 10 feet you're going 25.23 feet/second which rounds down to 150 feet per round. So according to the rules ... hmm ... at first I was going to say you're never going to hit that speed but then again you're doing things other than just moving, so with a dash the average person could go 60 feet per round. Still less than half unless you're a monk.

But a sprinting (move + dash) dragon would be 160 feet/round so close to that speed. That means, according to D&D rules, they'd be going about as fast as you are falling after 10 feet. Therefore they take 1d6 damage. Running into a wall is going to hurt. It theoretically could even kill a commoner. It's hardly going to register with a dragon.

And ... now I have to quit procrastinating and go do something useful.

*A 150 pound person has a terminal velocity of 173 feet/s, an mammoth around 1,600 feet/s, a squirrel reaches terminal velocity at around 10 feet at about 14 feet/s. It's likely even lower for the squirrel because they can increase their air resistance more effectively than human or mammoth.

 

[Clint_L]

Sorry Oofta, but I don't think your conclusions make sense, here. That dragon is going to be packing a LOT more force than a person would when they hit the wall, and that energy has to go somewhere...and if the wall is completely hard and immovable, like a wall of force, then all that energy is either going back into the dragon or being released as heat - probably a combination of the two. Contrary to your suggestion, the dragon would sustain far more damage than a person would from that impact. Conservation of energy, and all.

This also tracks common sense - we've all seen a bird hit a window at a fairly high speed and recover relatively quickly, I'm sure (sadly not every time, but often). But imagine what would happen to a person who hit a wall at 30 kmph.

Here's another example: ever been on a ferry? What happens when they hit the dock, even though at that point they are going as slow as possible? There is so much energy released that the ferry bounces back, and the dock has to be designed to do likewise or it would be quickly destroyed.

Now imagine that instead of the dock, the ferry is running into a 7mm steel edge, and doing so at full speed, and you start to see the implications of wall of force as an offensive weapon.

Edit: okay, I used an online calculator, and assuming a 10 metric ton dragon moving at 50 kmph, they will hit the wall of force with about 980000 joules of energy. That is a LOT (more than a hundred times what a large person would generate). If they hit it edge-on, then a huge amount of that energy is being directed back into a very small area of the dragon, much worse than if they had impacted a broad surface to distribute the release of energy throughout their entire body. Either way would be catastrophic, but I am confident that in any kind of real world scenario that dragon would be split in two by the hitting the edge.

Now obviously D&D is not a simulation game, plus there's magic (dragons can also fly, for example). But I would not just want to hand-wave that kind of damage unless, as cleverly suggested above, we establish that the wall of force is also some kind of magical energy absorber, and not just a hard surface. Which I think will become my house rule.

Edit: how much is 980000 joules of energy? Well, a big game gun, like one used for hunting elephants, fires bullets that hit with around 5000 joules of energy, or roughly .5% as much. So yeah, it's a lot.

 

[Oofta]

Sorry Oofta, but I don't think your conclusions make sense, here. That dragon is going to be packing a LOT more force than a person would when they hit the wall, and that energy has to go somewhere...and if the wall is completely hard and immovable, like a wall of force, then all that energy is either going back into the dragon or being released as heat - probably a combination of the two. Contrary to your suggestion, the dragon would sustain far more damage than a person would from that impact. Conservation of energy, and all.

This also tracks common sense - we've all seen a bird hit a window at a fairly high speed and recover relatively quickly, I'm sure (sadly not every time, but often). But imagine what would happen to a person who hit a wall at 30 kmph.

Here's another example: ever been on a ferry? What happens when they hit the dock, even though at that point they are going as slow as possible? There is so much energy released that the ferry bounces back, and the dock has to be designed to do likewise or it would be quickly destroyed.

Now imagine that instead of the dock, the ferry is running into a 7mm steel edge, and doing so at full speed, and you start to see the implications of wall of force as an offensive weapon.

I was talking about running into a flat wall. Running into a 1/4 inch thick piece of steel edge on would certainly hurt a person, but they wouldn't be split in two.

The problem is you're comparing real world versus fantasy. A dragon cannot exist for multiple reasons, they have to have some sort of magical reinforcement in order for them to be as large and mobile as they are. A T Rex could only walk at about 3 mph (sorry Jurassic Park) because otherwise it would break it's bones. The big sauropods were likely even slower.

So I assume that pound for pound, a dragon is a lot more resilient than animals. Whether that's supernaturally strong bones or just some kind of inertial dampening, they cannot be judged by real world standards. I lean towards the inertial dampening explanation because otherwise dragons would be quite clumsy since it would take far too long to change direction or even attack with various body parts. Your ferry can't turn on a dime or suddenly reverse direction but a dragon has no such restriction since their dexterity is about the same as a human's.

Which all really comes down to the DM making a judgement call. I've given my reasoning and ruling.

 

[greg kaye]

... make sense, here. ...

in D&D?

We all might think that there'd be a multiple to the damage received when hitting a non-flat surface but here's at least one case where that doesn't happen.

 

[greg kaye]

... That dragon is going to be packing a LOT more force than a person would when they hit the wall, ...

I'm not sure if weight is ever a 5e consideration RAW but that makes clear real-world sense.
D&D also rarely gives weights for creatures but some of its offerings seem on the light side. For instance, I'd previously noted that its ogres, statistically, would be relatively skinny.
Anyway, here's an extract from the third edition's Draconomicon:

 

[Lanefan]

Oof, thanks Gary for more of your "hidden rules", lol. This is right up there with "Assassins can learn how to make poisons, but don't you dare tell them that they can, those dirty, dirty players."

Keep in mind the DMG came out a year after the PH, meaning a year more play experience went into things and he'd had time to add in some rulings.

 

[Lanefan]

Take Freedom of Movement, a spell designed to let you move and attack in water without penalty; there are some DM's out there who say the spell prevents swimming, and instantly causes you to fall through water to the bottom, which can make it suddenly very useless when fighting foes at sea who can now swim above you as if they had flight (and depending on the depth, your DM might decide to ad hoc damage for the "crushing depths of the sea floor"), lol.

I've made this exact ruling for Rings of Free Action, such that falling out of a boat is like falling out of a plane.

 

[Lanefan]

That's not in the spell's description:
View attachment 288064
Things hitting the wall certainly stop dead, but I'd think that this is because they hit a wall.

When they hit the flat side, yes. It's clear the designers only thought of that part and didn't really bother to consider what happens if something runs into the wall edge-on.