The ability to gain speed quickly is crucial for survival, but there’s a limit as to how rapidly an animal can accelerate. Researchers wondered whether the “wheelie” problem experienced by cars during a drag race could be a factor in four-legged animals’ ability to speed up. They came up with a simple mathematical model… to see how fast a quadruped could accelerate without tipping over backward. The model predicts that the longer the back is in relation to the legs, the less likely a dog is to flip over and the faster it can accelerate. Then the researchers tested the model by going down to the local track, London’s Walthamstow Stadium, and video-recording individual greyhounds as they burst out of the gate in time trials. The acceleration approached–but never exceeded–the limit predicted by the model
Archive for June, 2009
Over at incoherently scattered ponderings, there’s a post on safety at academic labs, which links to an article at Slate about an explosion at a lab which killed a worker, and discusses the difference in safety standards for students vs workers, and academia vs industry.
Why the difference between industry and academe? For one thing, the occupational safety and health laws that protect workers in hazardous jobs apply only to employees, not to undergraduates, graduate students, or research fellows who receive stipends from outside funders. (As a technician, Sheri Sangji was getting wages and a W-2. If she’d been paying tuition instead, Cal/OSHA could not even have investigated her death.)
I had not realized that students aren’t covered, but the disparity between the described situations is not surprising. I’ve spent time in academia (grad school) and worked in national labs (the NanoFabrication facility at Cornell, TRIUMF in Canada), and my current government job is a confluence of being industry/government and a quasi-national-lab (though not formally recognized as such). And I have to concur: lab safety in a university setting is not formally the priority is is in those other places. Academic safety leans far too much on the involvement of the PI, and leaves way too much to chance. A key difference of academia is that students are … students — they are still learning, and one cannot assume that they have the requisite experience to know much about the finer points of safety.
I had no idea water rights apply/applied to rainfall.
Neither a spherical Michael Jackson nor a point Michael Jackson is assumed.
Why do so many states require only two years of math in high school?
We have anecdotal evidence that suggests that students who actually take math for all four years of high school do better in math here than those who don’t. We also have anecdotal evidence that bears crap in the woods. Why the hell do the high schools only require two years of math?
And there is followup at Uncertain Principles
There is a lot of discussion, so I may have missed someone raising the following point:
People who take four years of math and do well are probably good at math. Whatever distribution of students took the math for two years, I’d bet that it’s not the same as the distribution who took it for four. I’ll bet the players who go out for (pick your sport) do better at that sport in gym than the players that don’t, because you tend not to pursue and enjoy an activity if you suck at it.
The discussion seems to be dealing more with the other reasons why schools don’t require four years of math. I can ignore that for a moment and still assume an ideal case not limited by the availability of teachers or caused by bureaucracy. To me, the proposed solution embedded in the rhetorical question is not the head-slap obvious conclusion.
Apparently “Swan flu” is a common search term, supposedly a mistake by people researching swine flu, but I think we know what’s really going on.
You don’t have the flu. You’re just hot for this blog.
Created as the ultimate spy plane, the SR-71, which first took to the air in December 1964, flew reconnaissance missions until 1990, capable of hurtling along at more than Mach 3, about 2,280 miles per hour—faster than a rifle bullet—at 85,000 feet, or 16 miles above the earth. It is the fastest jet-powered airplane ever built.
Mach 3 is about 2280 mph … at sea level. But it varies with
density altitude, so at 85,000 feet, it’s about 2000 mph. The speed of sound, i.e. Mach 1, is not a constant of nature — it’s defined by the conditions (as opposed to the speed of light, which is c in a vacuum)
If anyone is missing the recently-late Billy Mays … you can either tune into cable and wait 5 minutes, or go here:
(I am not lamenting his loss any more than the other ~150,000 people that die every day)
By 2050, world population is expected to exceed 9 billion people, up from 6.5 billion today. Already, according to the report, a gap is emerging between agricultural production and demand, and the disconnect is expected to be amplified by climate change, increasing demand for biofuels, and a growing scarcity of water.
Another video, reminiscent of the viral popcorn-popped-with-a-cellphone video I discussed a while back
And, in fact one of the response videos is with popcorn
Objections: One is electrostatic. Matt has been discussing static charge distributions recently (here and here) and it’s very important to note that he’s discussing charge distributions on conductors — the charges can easily rearrange themselves. But in these video examples, the people and the targets are not conductors. So while you might build up some static charge on a person (in a very questionable display of boys gleefully rubbing other boys with balloons. Not that there’s anything wrong with that, if that’s who you are, balloon-fetish-freaks). A discharge to another insulator just isn’t going to send the energy where you want it to. A small discharge will even out the potential difference, and you’re done. A full discharge needs to be to a conductor, preferably a grounded one.
Speaking of sending the energy, how much energy are we discussing here? I’m not sure how much energy it takes for an eggsplosion, but I’m guessing we’re talking well above a few Joules. Accounting for my slight overestimation of the water content in the earlier popcorn analysis, it probably still takes somewhere north of 10 Joules of energy to pop a single kernel. Can we get anywhere close with static charge?
The energy stored in a capacitor is 1/2 CV^2. The capacitance of the human body is a few hundred picofarads. Let’s be generous and say it’s 2,000 picofarads (pico is 10^-12). How much of a potential difference do we need for 10 Joules? Do the math — it’s 100 kV. A few kV makes for a painful spark when discharging to a doorknob. A 5 mm spark between conducting spheres happens at about 16 kV. A realistic spark leaves us at significantly less than a Joule of energy.