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Can casting feather fall on a ballista bolt make it travel farther?

Feather fall makes objects fall 60ft/round, but only vertically. So, if I cast it on the ammunition then fire, it would fall only 60 ft/round, meaning that it will fly farther because most of its velocity is horizontal, not vertical. I suspect that from a tower, it can hit the walls of a castle 1,200,000 feet away.

Would this work? Assume a caster level of 20, so it can be fire from a (20×60 =) 1200 foot-high tower and travel horizontally ×1000 faster than vertically.

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Note on Bonus 1: Changing the size and mass of the arrow shouldn't affect the overall momentum, which is the only thing that matters for causing damage to e.g. walls. So your arrow will expand, but slow down incredibly, and the damage will be the same as if you just fired a normal ballista bolt. –  ioanwigmore Aug 31 '12 at 13:20
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Please don't ask "bonus" questions. I've removed them to focus this on feather fall only. If you have separate questions about unrelated spells or situations, ask them separately. –  SevenSidedDie Aug 31 '12 at 16:26
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If feather fall reduces weight instead of negating gravity, then your bolt will go less distance, stopping when air resistance overcomes it - like firing a big feather. –  mxyzplk Sep 1 '12 at 17:54
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@mxyzplk The (3e) spell makes no mention of its method of operation at all. This is why I hate seeing physics applied to game rules that aren't designed with physics in mind! Or maybe I just hate seeing game rules that are at all simulation-y but aren't designed with physics in mind… (NB that AD&D does say: mass becomes that of a feather. Yay prose-based rules systems that let you creatively infer things.) –  SevenSidedDie Sep 1 '12 at 18:11
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@TimLymington: Air resistance will be the same regardless of the effective mass of the arrow. But the arrow's momentum won't be. An apple and a feather may fall the same way, but they don't get blown about by the wind to the same extent. –  Tynam Oct 6 '12 at 10:48

4 Answers 4

up vote 5 down vote accepted

If you can cast Feather Fall on an arrow, then it's easy to determine the ranges which it can be fired.

Each round, the arrow will drop 60ft, and travel roughly 1200ft horizontally (value taken from Yahoo Answers)

So if you fire from on top of a 1200ft-high tower, your arrow will fly for 1200/60=20 rounds, travelling a total of 20x1200=24,000 feet. This is assuming there are no hills, uneven terrain, and no wind to affect the flight of the arrow.

So in conclusion, the arrow will fly 24,000ft, not 1,200,000ft like in the question, and it will also take 20 rounds to reach its target.

[Note, this is for a longbow arrow, not a balista arrow, but I doubt there will be much difference in flight speed.]

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You saying an arrow falls 1ft while flying 20 ft ? –  huseyin tugrul buyukisik Aug 31 '12 at 13:14
    
Feather fall says it falls 60ft in 6 seconds, the horizontal distance does not affect that at all. Faster/slower arrows will travel further/shorter in 6 seconds, but still only fall 60ft because of the spell. –  ioanwigmore Aug 31 '12 at 13:23
    
Yep, this, but ignoring the aiming skill of the ballista operator. Accurately hitting a target 4.545 miles away, even a castle, is going to be a helluva miracle. There's a reason that D&D's maximum ranges are effective ranges, not maximum possible distance. –  SevenSidedDie Sep 1 '12 at 1:23
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-1 for not taking into account the possibility of a round world and the Coriolis effect. (Just kidding..) –  dlras2 Sep 1 '12 at 16:50
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@starwed The longbow is a different weapon. It's used en mass for indirect fire at that sort of range. As a result, its real-world maximum effective range and its real-world maximum range are the same. –  SevenSidedDie Sep 1 '12 at 18:15

My typical approach is to reward creative thinking without breaking the rules.

So, in my owner personal opinion, I would add 50% range increment to the weapon, but it deals -1 damage for each increment over the normal maximum. This still caps it out at 10 range increments, but within that allows for better accuracy at further distances. This way we don't have to worry about a ballistae bolt landing 5 miles away, but the player doesn't feel like they can't be creative. It is a good idea.

Another way to rationalize this limit, if a player is being difficult, is that wind patterns at the point of firing will not be the same 100 ft., 1,000 ft., or 10,000 ft. away. Cumulative interference over a large distance will eventually cause the bolt to unbalance, wobble, and fall (slowly, of course) unless there is some sort of flight control. Additionally, the force at impact is determined by the momentum left in the bolt, which declines over time due to wind resistance. This means that the further it goes, the less damage it does on impact.

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I would suggest that your DM borrow the rules from the Pathfinder version of Feather Fall:

This spell has no special effect on ranged weapons unless they are falling quite a distance. If the spell is cast on a falling item, the object does half normal damage based on its weight, with no bonus for the height of the drop.

The salient point, in this case, being the "no special effect on ranged weapons" part. Magic spells don't typically obey Newton's laws.

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That's identical to the 3.5e spell's wording. That clause is there to prevent feather fall from being used as a defensive spell against incoming fire, hence the "unless it's falling quite a distance". Clearly the spell does effect ranged weapons (it even says how to handle damage from falling missiles), it just doesn't have a special "make them fall out of the air in front of my nose" effect. (This is a clause put in to address the arguments people had in AD&D, which might not be obvious coming at 3e fresh.) –  SevenSidedDie Sep 1 '12 at 18:20
    
If you want to get into semantics, there is nowhere in the rules that says a projectile from a ranged weapon is considered "falling". I wouldn't allow it as a DM - it's clearly a fuzzy rule description exploit, not part of the intent of the spell. –  RMorrisey Sep 3 '12 at 2:49
    
It's more of a historical argument than a semantic argument. Regardless, there's still a problem with suggesting borrowing from the "Pathfinder version" of the spell, since the text of the 3.5e spell is identical – no borrowing is necessary. –  SevenSidedDie Sep 3 '12 at 3:07

The following answer is from a RAW viewpoint - detailed physics not considered:

You can't cast Featherfall on ammunition loaded in a ballista as the target of the spell must be free falling. You would have to wait until it was fired, and the caster would need to be in Close range (25ft + 5ft/2 lvls) (in your example 75 feet). As the spell is instantaneous that should be okay.

Ballistas have a range increment of 120 feet so the maximum range is 1200 feet (10 range increments). I would assume at that point the arrow has run out of forward momentum/movement and would then float to the ground if it hasn't hit something. So no real advantage.

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That's not how ballistics works -- even when ignoring air resistance, and assuming a constant forward momentum, you get a maximum range. Air resistance will reduce it a bit, but it will still have forward momentum when it hits something at max range. Combining physics and magic is seldom sensible, but feather fall should help a projectile travel further. Just like you can throw a paper airplane quite far, but it's the spell, not wings, causing lift here. –  starwed Aug 31 '12 at 15:43
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Yes, the maximum range in D&D is intended to abstract maximum effective range, so it doesn't represent the maximum distance it can travel. If we're inviting physics in the back door, then we have to unpack the physics abstractions in the rules. On the other hand, if you intended to give a RAW answer that doesn't meddle with physics, you might want to edit to introduce this answer with something like "this is the strict, non-physics interpretation of the rules". –  SevenSidedDie Aug 31 '12 at 16:32
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Sorry, I'm no physicist and won't try and answer a question pretending I am. However, my basic understanding is that projectiles are fired in an arc, reach a maximum height where gravity wins the battle between going up and forward, to down and forward and then accelerating the object until it arrives, except in this case we've reduced that significantly so it won't deliver as much damage as it won't be travelling anywhere near as fast. So it might go further but would be a lot less effective in delivering damage. I think you'd be better off going higher up and skip the spell. –  jsecker Sep 1 '12 at 0:01
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+1 for pointing out that featherfall must be on a free falling target. -1 for poor reasoning on what happens afterwards. Net: 0. –  Ichoran Sep 1 '12 at 18:10
    
If you fire a projectile in an arc then it is not "free falling" when fired and does not qualify as valid target for Featherfall. –  jva Sep 2 '12 at 9:36

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