Crazy vehicle physics?

[Arravis]

Ok guys, I'm working on transfering the vehicle rules (so we could do some custom vehicles later on, etc) from the Arms and Equipment Guide to 3.5 and I came across this little tidbit:

"Leaving a Moving Vehicle: Whether you jump or get pushed, sometimes you leave a vehicle while it’s moving. Hitting the ground deals 1d6 points of damage per 10 feet of speed (Reflex half DC 20). Regardless of the save result, such a character is prone unless she succeeds on a Tumble check (DC 15 + 1 per 10 feet of speed)."

Physics was never my strong point but it doesn't make sense that falling out of a vehicle should cause the same damge as falling from a height. Just doesn't seem right to me that if a wagon moving at 30 causes 3d6 damage to a character leaving it. Seems a bit nuts to me... am I completely off on this? Any opinions on this?

 

[Jack Simth]

Physics and Damage don't mesh well.

You can say you have a particular impact energy. But does that equate to damage?

You can say you have a particular impact speed. But does that equate to damage?

What is Damage? What is HP? Without answering those questions, it's hard to say how much damage a given activity should do realistically.

 

[Dannyalcatraz]

Physics was never my strong point but it doesn't make sense that falling out of a vehicle should cause the same damge as falling from a height.

You don't just have the kinetic energy from falling vertically, you also have some from moving horizontally.

When you fall from a moving vehicle from X height, you're travelling a curved (half of a parabolic arc) path in the same time it would take a weight in a vaccuum to fall vertically from X height. You're travelling a longer path in the same time, thus, you're moving faster, and thus, you take a bit more damage.

How much more?

Beats me- I'm no mathmetician.

 

[tomBitonti]

Yep, that doesn't make sense

Physics was never my strong point but it doesn't make sense that falling out of a vehicle should cause the same damge as falling from a height. Just doesn't seem right to me that if a wagon moving at 30 causes 3d6 damage to a character leaving it. Seems a bit nuts to me... am I completely off on this? Any opinions on this?

Yah, that doesn't make sense.

You should take damage for the height fallen, and then some for brushing against the
ground.

If you fell against a very smooth and slippery surface, say, the surface of a frozen lake,
then you should take *no* additional damage for the horizontal motion. (Unless you slide,
at speed, into a horizontal obstruction later on.)

If you hit a *very* sticky surface (say, a human sized fly strip), then you should probably
take about the same amount of damage as if your horizontal speed were vertical. The
physics looks a little different, but the imact event will need to dissipate all of the energy
in a short amount of time, so I'm thinking about the same amount of damage.

Middle case, you will bounce, slide, or tumble along horizontally, at each impact scraping
the ground and taking some damage from that, and other damage as your horizontal
movement is partially transformed into a spin. I'm not quite sure how that would work, but
I imagine that there would be a number of smaller impacts as you tumble unevenly along
the ground.

If you somehow manage to not spin, you'll have a long painful scrape. If you were wearing
heavy clothing, this is perhaps not so bad. If you are lightly clothed, that will be a lot of
bloody scrapage.

(I've actually done this while skiiing. Clipped someone at speed, with a long slide in
the snow afterwards. Clipping the other person knocked the wind out of me, and I was
pretty stunned and shaken up by the whole event, but came out with no harm that
lasted more than about 10 min. I imagine I was going 30-40 mph, or 45-60 fps.)

Note that 60 mph is about 88 feet per second. I usually approximate it as just 90 feet
per second, as that makes the math simple. A world class sprinter can run 300 feet
in ten seconds, for an average of 30 feet per second, or about 20 mph. That's about
one seconds of downward accelleration, or about 15 feet fallen.

Meaning, if you are very, very, good, you should be able to handle being pushed out of
a car going up to about 20 mph by hitting the ground running.

Btw, that makes going 60 mph *about* the same as falling 120 or so feet. Which
is to say that 60 mph is quite fast. You *don't* want to be hit by a car going 60.

 

[Plane Sailing]

Ok guys, I'm working on transfering the vehicle rules (so we could do some custom vehicles later on, etc) from the Arms and Equipment Guide to 3.5 and I came across this little tidbit:

"Leaving a Moving Vehicle: Whether you jump or get pushed, sometimes you leave a vehicle while it’s moving. Hitting the ground deals 1d6 points of damage per 10 feet of speed (Reflex half DC 20). Regardless of the save result, such a character is prone unless she succeeds on a Tumble check (DC 15 + 1 per 10 feet of speed)."

Physics was never my strong point but it doesn't make sense that falling out of a vehicle should cause the same damge as falling from a height. Just doesn't seem right to me that if a wagon moving at 30 causes 3d6 damage to a character leaving it. Seems a bit nuts to me... am I completely off on this? Any opinions on this?

Your right, it is a bit nuts.

Falling damage increases linearly with height you fall, but that isn't a linear relationship to your velocity.

This rule is suggesting that the damage is a linear relationship to velocity.

To harmonise them it should either:

be 1d6 per 10ft of speed for moving vehicles (and then work out the speed you are after each 10ft of fall - shouldn't be too difficult to make up a little table and calculate the falling damage per 10ft. It would probably be surprisingly high).

or be 1d6 per 10ft of fall, and again do the little speed table and increase the damage from a vehicle fall when the vehicle velocity reaches each threshold equivalent to an additional 10ft of fall.

Cheers

 

[Arravis]

To add to this, it seems that falling off of a horse only causes 1d6 points of damage, regardless of the speed it's traveling at.

 

[Primitive Screwhead]

I think a potential better means is to make portions of the damage non-lethal based on the angle of attack and 'stickyness' of the ground.

Fer instance:
horizontal, up to 5D6 is non-lethal
30 degrees, up to 3D6 is non-lethal
60 degrees, 1d6 is non-lethal
{tumbling skill still can convert another d6 to non-lethal)

The type of ground affects the Reflex save and tumble checks,
Very Soft, such as fluffy snow or soft sand +8
Soft, normal snow or beach sand +4
Normal +0
Rocky, -4
Jagged, -8


This doesn't come close to real world physics, but then again neither does 'hit points'

 

[Christian]

Well, let's see ... 90' per round is 15' per second, or about 10 miles per hour. (Not bad for a human running full-speed in plate armor, but I digress ...) That's 9d6 damage, or the same as falling 90'. So evidently, falling from a car going 10 MPH is about as damaging as falling 90' onto a hard surface.

Huh.

 

[Dannyalcatraz]

Just an update, of the unfortunate variety...

Here in D/FW, we just had a teenager die from a fall from car-surfing.

Allegedly, the car was going around 10mph & the surface she hit was concrete.

Was it the same as a 90' drop? Probably not- in all likelyhood, she just fell funny. And I know from 2nd hand experience (a buddy who likes motorcycles) that its possible to "put your bike down" at 60MPH and walk away.

Final Advice: Find a rule you like and stick with it- you won't be able to model the entire process of falling from a vehicle with any accuracy without using a LOT of variables...

 

[Plane Sailing]

Just an update, of the unfortunate variety...

Here in D/FW, we just had a teenager die from a fall from car-surfing.

Allegedly, the car was going around 10mph & the surface she hit was concrete.

Was it the same as a 90' drop? Probably not- in all likelyhood, she just fell funny. And I know from 2nd hand experience (a buddy who likes motorcycles) that its possible to "put your bike down" at 60MPH and walk away.

Final Advice: Find a rule you like and stick with it- you won't be able to model the entire process of falling from a vehicle with any accuracy without using a LOT of variables...

One of the ways that I've handled it in the past is to say that when you take falling damage you take 1d6 lots of falling damage - to reflect the excessive variability of real life where, as you say, some people fall 10ft and die, others fall 1000ft and walk away.

having a random multiple of the damage accounts for 'died of multiple injuries'.

I'm not claiming it works for all situations, but it worked well for me in D&D (and a variant works well in damage save situations like True20 too)