D&D 5E Wherein we discuss spells and other magical things.

[Sorcerers Apprentice]

Do you distinguish between violent movement of the sphere caused by impact with the ground, and violent movement of the sphere caused by impact with a dragon's tail for example?

A dragon's tail slap doesn't actually cause violent movement in D&D, just bludgeoning damage. The same with a Giant with a huge golf club; if he hits a fighter with that the fighter will be standing in the same spot after taking damage, so I don't see why the sphere should work differently if hit.

It seems clear that the workings of the Sphere is more complex than simply turning inertia off. Good old Otiluke probably spent quite a while calibrating the spell to get it exactly right. In the spirit of "rulings not rules" I think it's up to the DM to rule however he wants in the edge case of a Resilient Sphere falling off a cliff. I think the most fun would be to have the sphere bounce around uncontrollably for a while after hitting the ground, but I can see the charm in having the wizard go splat against the inside of his own sphere.

 

[Oofta]

No, it doesn't. But that's a description that is consistent with the known and uncontroversial behavior of the ORS.


Your understanding of Newtonian physics seems...flawed. The concept that the ground is applying equal and opposite force to the falling object is Newton's 3rd!



(Emphasis mine.)

Just to clarify my statement, from my POV the ground is not adding any energy to the equation of the energy of the creature impacting the ground. All of the energy comes from the momentum of the falling creature.

And that is where I think we are splitting hairs. Yes, normally the ground would exert a force on a falling creature, I don't see that as the ground transferring energy to the creature.

In addition, if the sphere has no mass then you can exert no force against the sphere because force = mass X acceleration (a little simplified because force is really a vector). The sphere has no weight therefore it has no mass.

Which is why when the creature inside the sphere has their momentum stopped by the sphere it gets weird. The momentum should be transferred to the sphere but it can't because the sphere has no mass.

So the reason I see no reason to continue is that you haven't explained how it would work. No energy is transferred from the ground to the occupant. Much like there is no sound in a vacuum, force cannot be transmitted through an object with no mass. The energy of the momentum of the occupant must be transformed into some other type of energy, much like brakes on your car transform momentum into heat. In my world it would simply dissipate the energy harmlessly back into the ether where all magical energy comes from. But in any case, the occupant would still experience sudden instantaneous deceleration (assuming they have mass).

If you're just saying "I would rule this way because magic" that's fine. I'm trying to understand how it would work while breaking as few laws of physics as possible*. The only way I can have the occupant never take damage without hand-waving it is to say that when they are in the sphere for all practical purposes they have no mass. No mass, no momentum, no velocity. No velocity, no sudden changes in velocity which will cause damage to the occupant.

Anyway I apologize for getting frustrated, but if you're going to just insult my intelligence I get a little snarky.

*the sphere is basically a force field, and there is no known way to create a force field without breaking the laws of physics. A force field would have to be akin to the gravitational force, except that it can stop momentum in an instant and with a defined "boundary".

 

[Dannyalcatraz]

Just to clarify my statement, from my POV the ground is not adding any energy to the equation of the energy of the creature impacting the ground. All of the energy comes from the momentum of the falling creature.

And that is where I think we are splitting hairs.

This isn't splitting hairs, that position is utter science gibberish.

Third law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

The falling ORS & occupant cannot be the source of the deceleration force. The source is the ground.

Here's an illustration from a school book:

Newton's third law states that whenever one object exerts a force on a second object, the second object always exerts the same amount of force back on the first object. In the situation of a boulder falling to earth, the action force is the boulder exerts a force on the earth. The reaction force is the earth exerts a force on the boulder. The forces of the falling rock and the earth are equal and opposite but they accelerate differently because of their masses. Newton's 2nd law says mass and acceleration are inversely proportional. Because the mass of the earth is so huge compared to the small mass of the boulder, we don't sense it infinitesimal acceleration

 

[Oofta]

This isn't splitting hairs, that position is utter science gibberish.


The falling ORS & occupant cannot be the source of the deceleration force. The source is the ground.

Here's an illustration from a school book:

Thanks for the thoughtful and respectful reply. I appreciate the polite and open debate. Or not.

Whatever.

 

[steeldragons]

Next time I see a Resilient Sphere used in play, a Storm Giant is going to appear and chuck it as hard as they can in a random direction.

I'll roll 6d100s to see how many miles away it lands. But don't worry, the occupant won't take any damage.

So...how 'bout them Black Tentacles, ehnnh? That Evard's got some freak on, right there. Whaddaya think they're made of/coming from?

 

[Satyrn]

Next time I see a Resilient Sphere used in play, a Storm Giant is going to appear and chuck it as hard as they can in a random direction.

I'll roll 6d100s to see how many miles away it lands. But don't worry, the occupant won't take any damage.

So...how 'bout them Black Tentacles, ehnnh? That Evard's got some freak on, right there. Whaddaya think they're made of/coming from?

They're Cthulhu's spawn, living a long and fullfilling life, existing for an eternity in a blink of an eye. But also, each and every tentacle is a complete and perfect reincarnation of Evard's soul. This spell was his grasp at immortality, and now he is locked into an endless, incomprehensible battle to wrest dominion over the Far Realm from his father Cthulhu.

You can find the proof in e=mc2 (Evard = Magic times Cthulhu for the power over us squares)

 

[Sorcerers Apprentice]

This isn't splitting hairs, that position is utter science gibberish.


The falling ORS & occupant cannot be the source of the deceleration force. The source is the ground.

Here's an illustration from a school book:

The source of your confusion is that your are treating the sphere with wizard as a single body, when they are actually two separate bodies. So when the wizard splats against the inside of the sphere after the sphere has been stopped by hitting the ground, it's not the ground that's the source of the opposite force, but the sphere.

Since the sphere stops energy from going through either way, the ground will not be disturbed no matter how hard the wizard falls. That means all the energy in the fall will instead be absorbed by the wizard's body. Ouch.

That's of course unless Otiluke foresaw this problem and put in some kind of inertial dampener in the spell effect.

 

[schnee]

I don't think it's an exception. I think it is illustrative of the way the physics works in the sphere. Kinetic energy in the sphere operates normally. That includes inertia.

This is a game with elves, dragons, undead, and magic.

Leave your education at home, it doesn't matter here.

 

[Cognomen's Cassowary]

Since the sphere stops energy from going through either way, the ground will not be disturbed no matter how hard the wizard falls. That means all the energy in the fall will instead be absorbed by the wizard's body. Ouch.

I'm not sure this silly question about a silly game is worth continuing to hash out, but . . . If the sphere stops energy from going through either way, how will the energy of the fall get inside?

Edit because I just saw this:

The sphere has no weight therefore it has no mass.

This is not correct. An object cannot have weight without having mass, but an absence of weight is not evidence of an absence of mass.

 

[Oofta]

I'm not sure this silly question about a silly game is worth continuing to hash out, but . . . If the sphere stops energy from going through either way, how will the energy of the fall get inside?

Short answer? Magic.

My long answer:

Basic laws of motion: a boulder transfers momentum to the ground when it hits. There is an equal and opposite reaction. Energy is introduced into the equation by the momentum of the boulder striking the ground which pushes back with equal force.

However, we have a sphere that is weightless so therefore has no mass. It cannot have momentum because momentum = mass X velocity.

When the sphere falls off the edge of the cliff, the sphere does not technically fall (it has no mass and is unaffected by gravitational force). It is pushed by the occupant. The occupant accelerates towards the ground as normal because gravity sucks and it's been stated that the occupant can move the sphere.

The occupant of the sphere does not hit the ground. The sphere hits the ground, but it has no momentum so it does not transfer any momentum to the ground. There is no equal and opposite reaction because no momentum was transferred. It's velocity still becomes zero relative to the ground. Because magic.

The occupant still has momentum so they hit interior of the sphere. They cannot transfer momentum to the sphere, there can be no equal and opposite reaction in the standard Newtonian sense. They stop because magic.

If their velocity was high enough when they stop, and the stop is sudden enough they take damage. The damage does not originate from outside of the sphere - it happens because of the occupant's sudden deceleration caused by the magic of the sphere and the occupant's momentum.

There are all sorts of issues with ORS if you say you cannot transfer any energy from the exterior to the interior - basically the occupant would never gain momentum (change their velocity). You could not move the sphere because you could not move the occupant. Unless magic. If magic gives the occupant velocity, then magic can take reduce relative velocity to zero.

Or the occupant becomes effectively weightless (and massless) in which case all of the issues go away. You could even decide that the sphere offers no air resistance, since air is the one thing that can pass through the sphere. That also means that while you could pick up and carry the sphere, you could not throw it.