The claim is for short-duration -- i.e. not counting anything that happens after we reach my top speed. (Therefore under a second.) But the point of the question was what assumptions others would make or not make about the context of the claim. :-)
It sounds as though you figured out a context in which the claim could be accurate and then phrased your reply to probe whether the context you came up with is correct. Am I correct?
Am not sure about the human locomotion, but I would guess that even there the top acceleration has taken place long before top speed has been reached. But looking at the sprint racers it might be a good enough approximation for government work.
Yes, I figured it out. But you must admit that your framing of the question was rather obviousiating.
I don't know enough about motorcycles to be sure whether my guesses about their performance are correct. I have no idea whether I can out-accelerate most (or any) motorcycles.
Well, power to weight ratio is generally a lot higher on motorcycles than four-wheeled vehicles--my motorcycle has about 80hp and weighs 450lbs, ~60ft-lbs torque. 0-60 is usually under 4sec, often under 3, for more powerful sport bikes.
The point was to leave out that context and see who made what assumptions or noticed what was missing. :-) (Well, less to see who than to get a very very approximate impression of how many.)
Yes and yes, but not so much wow. This was definitely true when I was in shape; I'm pretty sure it's still true; I expect it to be true of most healthy humans, though I'm sure there are a few exceptionally slow ones.
The catch is that the race ends when one party reaches their top speed. (That is, the claim is only about dv/dt, not about v.)
Definitely true of myself when I was in shape; I think (with admittedly insufficient experimentation) that it's true of most healthy humans. But the scenario I'm thinking of is both at a dead stop, waiting for the "go" signal, and measuring peak acceleration (or even average acceleration over the time it takes to reach any given speed that whomever you're measuring can reach).
But it's interesting that you did immediately go to the context I was thinking of, (i.e., "the espeaker is on foot"). That was what I wanted to test -- how many people would do that, how many would make some other assumption, and how many would complain that the context was missing.
Over the time required for the human to reach his or her top speed. (For even more dramatic results, use the peak instantaneous acceleration, probably about 0.15 seconds after the light turns green for most people, and (I'm guessing) earlier for trained sprinters.) So strictly speaking, maybe eight feet? But that'll give the human enough of a lead that the car will take another fifteen to forty feet (depending on the car and the driver, and of course the runner) to catch up again.
I kmow that a human in good enough shape can outrun a horse or a deer over a long enough distancel I don't know horses well enough to know whether I was ever quite that fit, but it was probably true for everyone on my college track team. Good parallel, looking at the other extreme time-wise.
Anyone who needs to express this in the car scenes usually has something to make up for. But some thoughts:
Cars are very fast (in the non-technical sense of "can achieve high rates of acceleration") nowadays. Motorcycles are yet faster. Even a Harley will usually be able to hang with the non-exotic cars; a sportbike will match/beat a high-end Porsche to 100 mph depending on the drivers. Bicyclists are out of luck except for the first ten feet, where their low mass means they don't overpower their frictive surfaces.
While unmodified humans can accelerate themselves in excess of one g briefly, it's not very useful for travel. No stock cars, to my knowledge, exceed 1g forward accel. Lateral 1g has been achieved, and under braking it's certainly possible. Motorcycles are closer to 1g, but rarely do people post numbers for street bikes (it's much more dangerous to test, so it's usually only done for track bikes).
0-15 mph acceleration is very different than 60-90 (hence horsepower as a useful measure). Many SUVs can drag race my car to about 20 mph, at which point they probably lose completely. Personally I feel many SUVs are overgeared at low speeds (i.e. accelerate too fast), causing accidents as people overdrive their braking capability. None of this is useful in daily driving; what is useful is the 35-65 region, to merge onto highways, and the 60-80 region, to pass.
"While unmodified humans can accelerate themselves in excess of one g briefly, it's not very useful for travel. No stock cars, to my knowledge, exceed 1g forward accel."
Exactly. When you wrote, "Cars are very fat [...] nowadays," I worried that maybe the difference between the cars of twenty years ago and the cars of today was greater than I'd noticed, but I guess not. *whew* So yeah, if the race is longer than forty feet, a lot of humans will be in trouble. But in general the human will pull noticeably ahead of the car before the car starts catching up.
Note that I did not inclde motorcycles because I just don't know enough about them. From what you wrote it sounds as though a human can still be expected to have a greater peak acceleration than a motorcycle, but it may not be readily apparent to the naked eye watching the race in real time?
I don't think I've ever managed to get anywhere near the acceleration on a bicycle that I can on foot. (A technique issue? An equipment issue? Simply the expected result?) Then again, as you pointed out, running isn't nearly as useful for travel over meaningful distances as the other options are, in general. (Okay, time travel dumps you pre-automobile, needing to get a message across terrain too rough for a bike and not on a railway, and too urgent for walking and too far for one horse, and there's no relay station to change horses. Running is the most effective means of travel then. But I'd be willing to call that a "special case".) If I'm trying to get somewhere, rather than prove a point about peak acceleration and mammal muscles, I'll take a bicycle or an automobile, or walk instead of run.
But the reason I posted my question was to see how many people made what assumptions about the context, or complained about missing context. (If I'd wanted to be more scientific about this instead of just going for a Very Rough Impression, I would've made comments screened and been much more careful with phrasing.)
I'll admit it took me a minute of thinking it through before realizing you probably meant what you meant. What you said is a *very* common thought in, especially the motorcycle crowd where folks often respond to street challenges, so it took a minute to shake off the preconceptions.
Another note: this ratio may change suddenly with the introduction of electric-motored vehicles. Gas engines don't pull from 0 rpm, so you lose some time in the first segment to clutch slippage as you try to match >0rpm to 0mph. Electric motors, conversely, have full torque at 0 rpm. Given that some prototype cars have ridiculous 0-60 times (4 seconds?) they might be accelerating fast enough off the line to match a human.
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It sounds as though you figured out a context in which the claim could be accurate and then phrased your reply to probe whether the context you came up with is correct. Am I correct?
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Yes, I figured it out. But you must admit that your framing of the question was rather obviousiating.
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2) Good for merging!
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Is person claiming to do this in his own car? On foot? On a bike? What?
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I make the claim for myself on foot.
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The catch is that the race ends when one party reaches their top speed. (That is, the claim is only about dv/dt, not about v.)
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But it's interesting that you did immediately go to the context I was thinking of, (i.e., "the espeaker is on foot"). That was what I wanted to test -- how many people would do that, how many would make some other assumption, and how many would complain that the context was missing.
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Sure. I'll buy it. Over what distance?
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I kmow that a human in good enough shape can outrun a horse or a deer over a long enough distancel I don't know horses well enough to know whether I was ever quite that fit, but it was probably true for everyone on my college track team. Good parallel, looking at the other extreme time-wise.
Context
Cars are very fast (in the non-technical sense of "can achieve high rates of acceleration") nowadays. Motorcycles are yet faster. Even a Harley will usually be able to hang with the non-exotic cars; a sportbike will match/beat a high-end Porsche to 100 mph depending on the drivers. Bicyclists are out of luck except for the first ten feet, where their low mass means they don't overpower their frictive surfaces.
While unmodified humans can accelerate themselves in excess of one g briefly, it's not very useful for travel. No stock cars, to my knowledge, exceed 1g forward accel. Lateral 1g has been achieved, and under braking it's certainly possible. Motorcycles are closer to 1g, but rarely do people post numbers for street bikes (it's much more dangerous to test, so it's usually only done for track bikes).
0-15 mph acceleration is very different than 60-90 (hence horsepower as a useful measure). Many SUVs can drag race my car to about 20 mph, at which point they probably lose completely. Personally I feel many SUVs are overgeared at low speeds (i.e. accelerate too fast), causing accidents as people overdrive their braking capability. None of this is useful in daily driving; what is useful is the 35-65 region, to merge onto highways, and the 60-80 region, to pass.
Re: Context
Exactly. When you wrote, "Cars are very fat [...] nowadays," I worried that maybe the difference between the cars of twenty years ago and the cars of today was greater than I'd noticed, but I guess not. *whew* So yeah, if the race is longer than forty feet, a lot of humans will be in trouble. But in general the human will pull noticeably ahead of the car before the car starts catching up.
Note that I did not inclde motorcycles because I just don't know enough about them. From what you wrote it sounds as though a human can still be expected to have a greater peak acceleration than a motorcycle, but it may not be readily apparent to the naked eye watching the race in real time?
I don't think I've ever managed to get anywhere near the acceleration on a bicycle that I can on foot. (A technique issue? An equipment issue? Simply the expected result?) Then again, as you pointed out, running isn't nearly as useful for travel over meaningful distances as the other options are, in general. (Okay, time travel dumps you pre-automobile, needing to get a message across terrain too rough for a bike and not on a railway, and too urgent for walking and too far for one horse, and there's no relay station to change horses. Running is the most effective means of travel then. But I'd be willing to call that a "special case".) If I'm trying to get somewhere, rather than prove a point about peak acceleration and mammal muscles, I'll take a bicycle or an automobile, or walk instead of run.
But the reason I posted my question was to see how many people made what assumptions about the context, or complained about missing context. (If I'd wanted to be more scientific about this instead of just going for a Very Rough Impression, I would've made comments screened and been much more careful with phrasing.)
Re: Context
Another note: this ratio may change suddenly with the introduction of electric-motored vehicles. Gas engines don't pull from 0 rpm, so you lose some time in the first segment to clutch slippage as you try to match >0rpm to 0mph. Electric motors, conversely, have full torque at 0 rpm. Given that some prototype cars have ridiculous 0-60 times (4 seconds?) they might be accelerating fast enough off the line to match a human.
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