What does a 50 lb rock do to a stone building from 500' up?

[Umbran]

The flyer can carry around 10 people. It's big! But they have limited ability to dig up and hoist rocks; they have lots of rope but no shovels or picks, so only what they find on an ancient volcanic mountain face.

For scale - a spherical hunk of granite 10" diameter will weigh in at about 50 pounds. Some volcanic rock is rather airy, but much of it is dense. If they have an entire mountain face, finding 10 such rocks should only be a matter of time, and not much at that.

 

[Janx]

there's another engineering problem. Granite is pretty stout stuff. The harder it is, the more likely to crack. I wouldn't want to drop a hammer on a granite counter or floor.

Volcanic rock is probably fluffier. So dropping an anvil or granite ball on a granite dome could very well crack it. Volcanic rock may shatter on impact, and the granite dome would be less damaged.

My rule of thumb on materials:
denser/solider material > airier, coagulated material.

I have no idea what kinds of rock you'll find at a volcano. I'm more imagining the crumbly pumice stuff.

So they're gonna want to drop something as solid as the granite. 2 dudes should be able to pick up a 100 pound rock, assuming they can find one to load it on the skysled.

 

[Dannyalcatraz]

And, as a tactical matter, you don't want to drop it straight down unless you're trying to hit a small target- dropping it while having forward motion (especially after a power dive to increase velocity) will maximize the damage the stone will do as it bounces, rolls and caroms. Angular velocity is a bitch.

 

[Janx]

And, as a tactical matter, you don't want to drop it straight down unless you're trying to hit a small target- dropping it while having forward motion (especially after a power dive to increase velocity) will maximize the damage the stone will do as it bounces, rolls and caroms. Angular velocity is a bitch.

good point, dive bombing to add vehicle speed + falling would probably be faster.

Even still, don't discount how much damage a 50 pound rock dropped will do. I wouldn't want to drop a 50 pound ball on my foot. I thought the force formula was f=m*v, but I am not a physics dude (Umbran will know the right answer).

In any case, it'll be many more pounds of force. Anything alive is NOT going to want to get love-tapped by a rock.

 

[Stormonu]

If I recollect correctly, rules-wise a falling object deals 1d6 / 200 lbs., +1d6/10 ft. fallen (max 20d6). So the rock would do 21d6 damage (ave 73 dam) to an object it hit. Structurally, a hewn stone wall (10'X10'X3') is going to be closest to your granite roof; with a hardness of 8 and up to 540 hp. Assuming the roof is probably only 6" thick (1/6 the hewn stone wall thickness), that'd give a section about 90 hp.

That likely means a single stone is probably going to go right through a stone-sized area (at least), and two stones will easily take out a 10'X10' area.

<EDIT> Checking further, with the stone weighing 50 lbs., it does 1d6 + 1d6/40 ft. fallen, so it would do 13d6 damage on impact (ave 45 damage). Still taking out the same area above with two good hits - if you want to use D&D's rules.

 

[Dannyalcatraz]

Even still, don't discount how much damage a 50 pound rock dropped will do.

Its not just about the force delivered, but how its delivered. Dropping a 50lb stone straight down, it will deliver all of its force straight down. It will make a single crater, basically.

Deliver that same mass traveling at an angle to the target, and it will bounce & roll and skip. Think of how cannon crews, aiming at opposing forces aimed low, not high, sending the cannonballs rolling through their foes as opposed to raining down upon them from on high. Many more casualties resulted.

 

[fendak]

I would just ask myself, what would be more fun? or how can I make this interesting? Forget about whether it works or not, I mean, If the players want to do it, and its somewhat feasible, I say do it but add some excitement. It could smash an entry in the roof and the rock destroys something valuable inside, or maybe upon breaking the seal of he roof the guardian is freed from protecting the building and is now free to hunt the land starting with the players mwhahaha.

 

[Wednesday Boy]

I would just ask myself, what would be more fun? or how can I make this interesting? Forget about whether it works or not, I mean, If the players want to do it, and its somewhat feasible, I say do it but add some excitement.

Exactly this. Don't let pinpoint accurate scientific details overshadow a clever idea that can lead to a fun, interesting story.

 

[jasper]

eww someone got science on my fantasy game. kill them. If stormou is correct use his damage. And they wimps. The cement bags my wife makes buy are 80pds. And I can load 10 into the truck without getting tired.

 

[Umbran]

Deliver that same mass traveling at an angle to the target, and it will bounce & roll and skip. Think of how cannon crews, aiming at opposing forces aimed low, not high, sending the cannonballs rolling through their foes as opposed to raining down upon them from on high. Many more casualties resulted.

Yes, but that's for using a cannonball against people. We're talking about damaging a building here - the projectile is probably not going through it at all, much less hitting multiple buildings beyond.

How to strike at the building depends on what you've got to throw rocks with, and how the building is constructed. In general, for maximum effective impact, you want your projectile to hit perpendicular to the surface you're hitting. If you're aiming at a wall, you want your projectile moving horizontally when it hits. If you're aiming at a roof, you want it coming in at right angles to that roof.

Mind you, dropping rocks off a stable platform is many times easier than trying to dive-bomb. Guys go to school to learn that stuff. Have your adventurers spent points on "Pilot magical flying machine" skill? Then don't expect them to hit the broad side of a barn on a dive-bombing run. Shooting arrows at goblins doesn't train you for this