Horsepower as a measure of attribute stuff

OgreBattle · Post by **OgreBattle** » Tue Apr 17, 2018 8:31 pm

So I'm reading the wiki article on horsepower and part of it calculates how a horse's peak performance is 14hp, while a human's is usually 2 hp with Usain Bolt achieving 3.5 hp

https://en.wikipedia.org/wiki/Horsepower

" 1993, R. D. Stevenson and R. J. Wassersug published correspondence in Nature summarizing measurements and calculations of peak and sustained work rates of a horse.[13] Citing measurements made at the 1926 Iowa State Fair, they reported that the peak power over a few seconds has been measured to be as high as 14.9 hp (11.1 kW)[14] and also observed that for sustained activity, a work rate of about 1 hp (0.7457 kW) per horse is consistent with agricultural advice from both the 19th and 20th centuries and also consistent with a work rate of about 4 times the basal rate expended by other vertebrates for sustained activity.[13]

When considering human-powered equipment, a healthy human can produce about 1.2 hp briefly (see orders of magnitude) and sustain about 0.1 hp (74.57 W) indefinitely; trained athletes can manage up to about 2.5 hp (1.85 kW) briefly[15] and 0.35 hp (260 W) for a period of several hours.[16] The Jamaican sprinter Usain Bolt produced a maximum of 3.5 hp (2.6 kW) 0.89 seconds into his 9.58 second 100-metre dash world record in 2009."

So it's force exerted x velocity achieved = power.

This website also has info on the horsepower of various animals
http://www.sjsu.edu/faculty/watkins/animalpower.htm

An ox has less horsepower 'cause they're slower.

So... does this mean charging with lance on horseback should be x4 more powerful than Ussain Bolt charging with a lance?

Username17 · Post by **Username17** » Tue Apr 17, 2018 9:37 pm

In raw physics terms, the difference in power between a rifle and a pistol or a lance and a spear is many multiples. In actual reality, people can be killed by a knitting needle or survive a 5 story fall. The amount of force required to make something "lethal" is just not very much, people can and do suffer fatal wounds from falling down from standing. Damage numbers are abstractions and almost 100% about playability and almost 0% about physics calculations.

-Username17

Longes · Post by **Longes** » Tue Apr 17, 2018 9:42 pm

Obviously in D&D you should measure your performance in cat power - how many domestic cats stacked on one another and equipped with magic collars of might fists you can fight off.

Whiysper · Post by **Whiysper** » Wed Apr 18, 2018 9:16 am

I feel bad for how much I want to adopt the 'HCKT' challenge rating system now (House Cat Kill Threshold). Dammit Longes.

Stahlseele · Post by **Stahlseele** » Wed Apr 18, 2018 9:42 am

If that is true, HP is a stupid measurement to use period. o.O
One HP is the power of one horse.
But one horse appearantly can have the power of 14 horses.
And a Human appearantly 2 to 3.5 . . so . . A human can have 28 to 39 HP?

Trill · Post by **Trill** » Wed Apr 18, 2018 10:02 am

no,
a horse can normally put out 1 HP, but for short intervals it can have up to 14 times that
a normal human can normally put out 0.1 HP, but can put out 1.2 HP for a short time
trained athletes can put out 0.35 for a long time and 2.5 HP for a short time
Usain Bolt managed to put out 3.5 HP briefly

Eikre · Post by **Eikre** » Wed May 02, 2018 10:19 pm

OgreBattle wrote:So... does this mean charging with lance on horseback should be x4 more powerful than Ussain Bolt charging with a lance?

No. At constant power, force diminishes proportionally to positive changes in velocity. At constant power, top speed is achieved when exerted force is equal to opposing forces, such as those of friction (intramuscular, from air, whatever).

At that point, the strength of a collision is based not on what force is being actively exerted on the second object (because that force is zero) but what forces are exerted by the transfer of kinetic energy, which is predicated on mass and velocity^2.

So if you care to look back at your table, you'll see that an ox is attributed with more power than a mule. The mule, however, is much faster and almost as heavy. A lancer on muleback would deliver a far mightier blow than one astride an ox.

tussock · Post by **tussock** » Thu May 03, 2018 2:54 pm

Part of the 200G you will experience on hitting the ground when falling from a very high height is in fact the 1G of regular old gravity you feel when you just stand on the ground. Same for swinging a bat and hitting a ball, or a head, the force applied through the impact does add to the force of impact, it's usually just quite small compared to the collision forces.

Which is why guys in military saddles and using a lance rode very heavy horses, rather than very fast ones. Some of that weight totally transfers with the right kit, and even a very small fraction of a very large horse is a good deal.

Ultimately, momentum matters way more than KE. High Energy and low momentum things help their case with projectile deformation once you get up to rifle bullet speeds, but medieval things are basically all momentum.

Thaluikhain · Post by **Thaluikhain** » Thu May 03, 2018 3:09 pm

tussock wrote:Which is why guys in military saddles and using a lance rode very heavy horses, rather than very fast ones. Some of that weight totally transfers with the right kit, and even a very small fraction of a very large horse is a good deal.

Ultimately, momentum matters way more than KE. High Energy and low momentum things help their case with projectile deformation once you get up to rifle bullet speeds, but medieval things are basically all momentum.

That's not particularly true. Different cavalry had different horses for different roles, many of them still using lances (or similar).

"Medieval things" covers a very wide range. Now, sure, for many of them, "let the weight do the work" is quite reasonably, but far from all of them.

Not sure how you can justify saying momentum is always much more important that kinetic energy. Especially as the difference between KE and momentum is v/2, they are closely related, thought far from identical.

Additionally, the heavier the weapon, the slower it is, and thus the harder to hit someone who doesn't want to be hit. Though, that is going on a bit of a tangent.

Eikre · Post by **Eikre** » Sat May 05, 2018 4:35 am

tussock wrote:Part of the 200G you will experience on hitting the ground when falling from a very high height is in fact the 1G of regular old gravity you feel when you just stand on the ground. Same for swinging a bat and hitting a ball, or a head, the force applied through the impact does add to the force of impact, it's usually just quite small compared to the collision forces.

Very well, as a point of order, I will of course concede. A powered object at terminal velocity will slow during the span of an impact event and of course this will mean that applicable force will increase from zero. The takeaway remains unchallenged that power is an indirect contributor to the force of a blow.

tussock wrote:Which is why guys in military saddles and using a lance rode very heavy horses, rather than very fast ones. Some of that weight totally transfers with the right kit, and even a very small fraction of a very large horse is a good deal.

Tussock, I want you to know that I am, essentially, rooting for you. I do believe you have the capacity to be Not Wrong. You've done it a couple times that I've noticed lately and I want you to understand that I admire the improvement. However, you still have a problem with laying out unsourced facts like these; when you do this, it's an arguments from your own authority, but the historical record demonstrates that your authority is absolutely invalid and holds no value whatsoever. It would be really excellent if you started to look for sources to cite when you made declarations like this. If you can't find a good one to validate you, then you need to reconsider your faith in the predicate you want to introduce. Yes, even if it means that you can't make the argument that you wanted to.

I absolutely realize the degree to which I'm patronize you, here, but the rest of the Gaming Den and I have honestly run out of ways to presume that this is something that you genuinely understand.

tussock wrote:Ultimately, momentum matters way more than KE. High Energy and low momentum things help their case with projectile deformation once you get up to rifle bullet speeds, but medieval things are basically all momentum.

No, Tussock, fuck, absolutely not. Why are you even opening your mouth to say this? This is 100% counterfactual, there is no way to award you even partial credit.

Momentum can tell you nothing about the force of an impact, because force is not a component of momentum. If I tell you that P = 200,000 kgm/s, then you might be looking at a single-gram bullet inflicting about a fourth of the devastation wrought at the very epicenter of the detonation of the first atomic bomb, or you could be looking at a gigatonne glacier that could be slowed from its mercurial crawl by a rubber band stretching fewer than five centimeters.

Energy (whether kinetic or internal) is literally the only thing that could possibly matter. Things break when bonds comprising that object are deformed so greatly that their spring-force outweighs their tolerance and they snap. That's force × displacement, which is literally the definition of change in energy.

Kinetic energy is ½mv². Velocity is exponentially more important than mass for creating a high impact. Reducing your velocity by 10% means you need to increasing your mass by 23.4% just to break even. Reducing it by 20% requires increasing your mass by 56%. For a cavalier, this also assumes an absolutely rigid rider and can put 100% of the horse's weight behind the tip of his weapon. He's not; the weight of the horse that he can harness in his swing is both fractional and capped. Trading a percent-decrease in velocity for even double that percent of an increase in your horse's mass is an immensely shitty fucking deal.

DrPraetor · Post by **DrPraetor** » Sat May 12, 2018 3:01 am

Momentum does matter because momentum is conserved.

In a head-on collision:
rider A is a 1000kg knight moving at 5m/s
rider B is a 250kg light cav moving at -10m/s.

Both have a kinetic energy of 25,000, right?

But the knight has a *momentum* of 5,000 while the light cav has a *momentum* of -2,500, which means post collision, the total system will have a momentum of 2,500.

Hand-waiving away elasticity and friction, they will both end up with a speed of 5m/s so the knight experiences acceleration of -5 m/s while the light cav experiences acceleration of +15m/s. Every action has an equal and opposite reaction, so the *forces* are the same but the consequences of the waves traveling through the two bodies as they accelerate are not.

EDIT: Ugh, sleepy. They will both end up with a speed of 2500 / 1250 = 2m/s. So the knight gets -3 m/s while the light cav gets +12m/s.

To take an extreme example: If I'm sitting in a building and you drive into it at 100mph in a car, the building and your car experience the same forces but a lot more of those forces are going to be transferred to your squishy body.

The injury inflicted by weapons depends on the deformation caused in the body of the target, which is typically a function of net acceleration and not the properly-speaking force of the blow. So Tussock is basically correct about pre-modern weaponry wanting to be heavy more than fast. Even with bullets, for a given quantity of propellant you penetrate armor better with a heavier projectile (although of course you have to pay for all that momentum as recoil.)

Yes, really. A larger bullet moves down the barrel more slowly, so the expanding gasses do approximately the same amount of work (which is a function of distance - the length of the barrel; there are differences due to cooling and so forth but these are tiny) but the same force is exerted for a greater length of time (which is a function of the mass of the projectile) and thus more momentum is transferred back up your arm.

erik · Post by **erik** » Sat May 12, 2018 3:42 am

DrPraetor wrote:

I feel for this guy. It is a palpable struggle in me between knowing the answer is obviously A, vs. How MUCH I want B, C or D to be something real.

Pariah Dog · Post by **Pariah Dog** » Sat May 12, 2018 4:05 am

I'm not sure if I'm more upset that he wasted a lifeline on what was one of the obvious easy questions or that 29% are either trolling this guy or really are this ignorant.

Although D sounds like one of those Saturday morning cartoon/action figure advertisements.

DrPraetor · Post by **DrPraetor** » Sat May 12, 2018 5:10 am

Gotta love those US customary units.

A llamathrust is, of course, the weight of a "standard" llama, which is defined as 4,926 troy ounces, or ~338 avoirdupois lbs. This is the thrust needed to *lift* a llama.

The zebraforce is slightly more than the typical zebra's weight, it's actually the force of a reference zebra *kick*, which is set by convention at 31,417 poundals or ~977 avoirdupois lbs.

Finally, the Donkeystrength is a unit of strength - the tension that a donkey can sustain before being torn apart in cross-section. It's standardized at 211 mmHg im the US, but if crops up in British usage they'll be using a "metricized" 30 kPa instead.

None of that is as insane as the acre:
https://en.wikipedia.org/wiki/Acre

Thaluikhain · Post by **Thaluikhain** » Sat May 12, 2018 2:54 pm

DrPraetor wrote: Finally, the Donkeystrength is a unit of strength - the tension that a donkey can sustain before being torn apart in cross-section. It's standardized at 211 mmHg im the US, but if crops up in British usage they'll be using a "metricized" 30 kPa instead.

I thought it was how many barrels you could throw at an Italian plumber when really angry.

Username17 · Post by **Username17** » Sat May 12, 2018 5:23 pm

Acres are indeed the weirdest fucking thing, being an amount of area equal to one unit of length you've never heard of that's about 20 meters by another unit of length that you have also never heard of that's about 200 meters. But for whatever reason, it's actually a fairly useful amount of space to talk about in terms of farm land. The hectare is used for similar reasons.

But like the acre, the hectare is made out of bullshit units you've never heard of. Technically, a hectare is one hundred "ares." There is pretty much nothing that ares are useful for, to the point that my computer doesn't even recognize it as a word. There are things you measure in square meters and there are things you measure in hectares and the fact that there is nominally another unit that is two orders of magnitude smaller than one and two orders of magnitude larger than the other is not helpful.

-Username17

Whipstitch · Post by **Whipstitch** » Sat May 12, 2018 6:40 pm

I've heard of furlongs, but only in the context of Monty Python skits and other period comedy routines which are used to explicitly set up a punchline about how nobody knows what the fuck is going on and none of the language makes sense. I routinely forget about chains though because that's not what the word chain should mean, you fuckers.

Pariah Dog · Post by **Pariah Dog** » Sat May 12, 2018 6:50 pm

Stahlseele · Post by **Stahlseele** » Sat May 12, 2018 9:12 pm

A furlong is a measure of distance in imperial units and U.S. customary units equal to one-eighth of a mile, equivalent to 660 feet, 220 yards, 40 rods, or 10 chains.

*boggles*
edit:
and it gets fucking worse x.x

Using the international definition of the inch as exactly 25.4 millimetres, one furlong is 201.168 metres. However, the United States does not uniformly use this conversion ratio. Older ratios are in use for surveying purposes in some states, leading to variations in the length of the furlong of two parts per million, or about 0.4 millimetres (1⁄64 inch). This variation is too small to have many practical consequences. Five furlongs are about 1.0 kilometre (1.00584 km is the exact value, according to the international conversion).

edit2:
further investigation into furlongs and leagues makes me as somebody who knows only the metric system deeply uncomfortable x.x

DrPraetor · Post by **DrPraetor** » Sat May 12, 2018 11:04 pm

I think all of these Simpsons quotes about units of measurement are causing us to lose sight of the chilling fact: Tussock was basically right about momentum being an important factor in degree of injury from various sorts of impacts.

https://twitter.com/simpsonsqotd/status ... 13?lang=en

erik · Post by **erik** » Sun May 13, 2018 12:23 am

No, we were kindly ignoring your support of Tussock. He didn't just say momentum was an important factor, he said it was more important than kinetic energy. Are you willing to back that claim?

Chamomile · Post by **Chamomile** » Sun May 13, 2018 1:06 am

DrPraetor wrote:

My first thought on seeing a question this obvious asked whenever there's any significant stakes (for example, a minimum of a hundred dollars in prize money) is always "wait, so this has to be a trap, right? Three of these things are immediately ridiculous. If horsepower was actually the correct answer, wouldn't they include at least one fake answer that seemed remotely plausible? And since they haven't, doesn't that suggest that one of these three crazy things is actually correct, and horsepower is the honeypot for people who don't know obscure units of energy?"

jt · Post by jt » Sun May 13, 2018 1:49 am

That would imply the contestant didn't bother watching any episodes of the gameshow he's on though. Anyone with a pulse can get to 64k.

Stahlseele wrote:further investigation into furlongs and leagues makes me as somebody who knows only the metric system deeply uncomfortable x.x

The key is to realize that the metric system is a system, and imperial measurements are not. It's just an unrelated collection of all the things that people traditionally use to measure various things. The imperial units are often better in terms of being a convenient sized measurement for the thing they're intended for. They're just garbage if you try to use any two in conjunction.

If you'd prefer an actual system using furlongs there's always the FFF system of units.

DrPraetor · Post by **DrPraetor** » Sun May 13, 2018 3:11 am

erik wrote:No, we were kindly ignoring your support of Tussock. He didn't just say momentum was an important factor, he said it was more important than kinetic energy. Are you willing to back that claim?

I have him on ignore, still haven't opened the post, and you can't make me.

But, yes. I thought I had. I mean, this is freshman physics, right?

In the example I gave, instead of 1000kg at 5m/s and 250kg at 10m/s, suppose we've got:
1000kg at (5 - ε)m/s
250kg at (10 + ε)m/s

The light cav will have more kinetic energy, and less momentum (if ε is small), and the results will differ only by some tiny amount from what I described.

Now, most of the time, momentum and kinetic energy are going to be highly co-linear, but generically speaking, the deformation tenser is going to be more sensitive to the momentum than to the kinetic energy.

As Frank pointed out far above, this shit gets very complicated (the key is "deformation tenser", over which you solve systems of equations depending on both momentum and kinetic energy) but if you have to choose between kinetic energy or momentum, you generally want momentum. This doesn't mean that momentum should be something you write on your character sheet, even in a video game (although weapon weight is the crucial attribute in this video game: http://www.retromud.org/proxy/help?=Combat/weapons ).

Even if Tussock is wrong about something else in his post, Eikre is wronger.

erik · Post by **erik** » Sun May 13, 2018 6:27 am

DrPraetor wrote:
erik wrote:No, we were kindly ignoring your support of Tussock. He didn't just say momentum was an important factor, he said it was more important than kinetic energy. Are you willing to back that claim?
I have him on ignore, still haven't opened the post, and you can't make me.

But, yes. I thought I had. I mean, this is freshman physics, right?

In the example I gave, instead of 1000kg at 5m/s and 250kg at 10m/s, suppose we've got:
1000kg at (5 - ε)m/s
250kg at (10 + ε)m/s

The light cav will have more kinetic energy, and less momentum (if ε is small), and the results will differ only by some tiny amount from what I described.

Fuck, it's been a long while since I dealt with highschool physics, so let me polish by brain for a minute.

*sigh* Your initial example was contrived to have a horse at 1/4 the mass with double the speed in order to have exactly equal kinetic energy.

If we contrive it another way, with the light horse being 500kg we can turn the tables and have equal momentum between a courser vs. a destrier. I googled a bit and seemed to find that 500kg vs 1000kg actually seem to be reasonable difference between light and heavy horsies, and the 2x speed may be fairly reasonable as well. Anyway. If you do that then the light horse has double the kinetic energy of the heavy horse, and when they impact, the heavier horse is on the losing side of the exchange as it receives more kinetic energy. Right?

p.s. I spent way too long reading articles about medieval horse sizes, uses, breed sizes and speeds. I don't remember why I even cared anymore.

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Horsepower as a measure of attribute stuff

Horsepower as a measure of attribute stuff

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