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Comment Re:Not bicycle powered? (Score 1) 123

I had the same reaction, that strapping a bicycle to it seemed totally irrelevant. But I guess you can bike down to the river, fly across, and continue biking. And if you don't mind burning some of your flight time you can use the batteries to power the bike. That gives you a combination of long ground range with the ability to fly over terrain or traffic at will. Cute. Too bad you're stuck with those big bulky fans all around it in cycle mode. If those could fold down compactly it would actually be a pretty practical combo to place on an electric bike. Well, of course that's setting aside the suicide-machine factor.

Final analysis: Darwin would approve.

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Comment Re:Noisy isn't it. (Score 4, Informative) 123

350 pound flight capacity minus 187 pound vehicle weight seems to indicate a 163 pound (74 kilo) passenger limit. Not great, but that's certainly not "anorexic child-size styrofoam dummy" either. I'm an adult male, I could get there if I cut out the peanutbuttercups and switched to diet soda.

Oh well, I guess that means I'm never going to be able to ride it. Diet soda is vile.
How about they work on inventing that? Soda that tastes like sugar-water without being sugar-water? Chuckle.

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Comment Re:all for it... (Score 0) 161

I'm all for police wearing cameras, provided that they cannot disable them. Unfortunately, it sounds like these can be disabled.

Don't think for a minute that the police intend to use the videos to clear suspects of wrongdoing, or to have documented evidence of police abuse that can be used in court.

It's the other way round: the police want video evidence to prove either that someone was rebellious during their arrest, or that the police didn't abuse them. People often try to blame the police in court to get off easy, and the police always has to prove they didn't use undue violence during the arrest. So videos are a good idea.

Unfortunately, it's a rather one-sided protection, as the police would never show videos in which they'd appear to have abused their powers. On the other hand, the lack of video itself would appear extremely suspicious in court I suppose, and would bolster a defendant's claim of police violence.

Comment Re:Contradictory Explanations (Score 1) 266

Well, that explains it - the little characters on the y-axis labels are 'h', not 'k', so I think you are reading it as three orders of magnitude too large

Doh! I know exactly what happened. That part was small and blurry, and in my initial scan over the graph, before I sorted out what the graph wa showing, it looked like "kp". A corner of my brain thought WTF is "kp", and I kept scanning elsewhere for information. I saw the speeds across the bottom and the thrusts on the left and I recognized the shape of the graph, then saw the HP vs MPH title at the top. I realized the different color lines had to be different engine inputs and I glanced back at that top-right box to confirm it.... that it was listing different HP engine inputs.... and that "k" from "kp" was still lingering in my brain. chuckle. So the blurry "h" was read twice, once as "k" and once as "h". The 250khp to 500khp power figures did strike me as unreasonably large, but I wasn't going to doubt the graph and my attention was absorbed on other issues. Sso without further consideration I just mentally filed it away as presumptively plausible values for a top end (?military?) engine.

the airflow through the propeller is slowed down... in this view the rotor is acting as a turbine, though a very unusual one in which the power is delivered through its thrust bearing, not by torquing the shaft.

Ohhhh noooooo! You didn't...... cry cry cry. LoL.
I follow your reasoning, and it is a kinda cool point, but oh jezus I wish you didn't make that analogy. The prop is NOT spinning as a turbine, and I know that you know that it's not spinning as a turbine, but someone is going to read what you wrote and think that one or both of us said it's a turbine. Newbies already have a hard time wrapping their heads around the idea that the prop is a fan. Any whiff of describing it as a turbine feeds badly into the exact "contradictory explanations" that set off alarm bells for you.

[the math/science] It's still at high-school level

I wish. You and I went to significantly above average highschools. The majority of U.S. highschool graduates only have one year of science, and it's generally something very generic like "Earth science" or something. It's only in the last few years that most highschools have moved to a two year science requirement, and even then, what percentage are going to include force-energy physics? I think the most common is a year of Bio, and even there most schools avoid or actively deny Evolution in that class :/

with regard to the exam question explanation. It says, correctly, that their formula implies that a totally inefficient device (alpha = 0) would travel at the wind speed.

What happened there is an entirely arbitrary and semi-self-contradictory cornercase crawling out of the simplifying assumptions. They started with a model of an ideal (frictionless) cart, and then to model a "real" cart they lumped together all losses... including rolling friction.... into one term alpha. They then set alpha to total energy loss... and they were still modeling that alpha on an ideal frictionless cart. They also silently and arbitrarily assumed wind drag *wasn't* zero, despite the opposite parallel assumption of zero rolling resistance. chuckle.

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