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Everything posted by wpenrose

  1. The answer is that the potential energy difference due to the elevated water source is turned into a pressure difference before and after the turbine. The pressure drop across the turbine is the force, and the transit through the turbine is the displacement. Force x displacement = energy. Turning your TV on draws current, and the turbine requires more force to turn. The slower flow allows the pressure difference to increase. Dangerous Bill
  2. Here's a puzzler for you. Actually, it stumped two eminent physicists that I know, for a short time. Yet the answer, once you realize it, is obvious. Imagine a hydroelectric plant. It operates from a body of water located at some altitude. The energy is 'stored' in the difference in height between the water at the top and the water at the bottom spillway. Now, when the plant is operating, you have a mass of water rushing down the tube to the turbines at the bottom. But the water entering the turbines is the same mass and velocity as the water exiting the turbines. So when you plug your TV into the turbine and it lights up, where does the energy come from? Dangerous Bill
  3. Yes. It's called hydroelectric power. Dangerous Bill
  4. Without knowing more about your battery types and your charger, I think there is only one safe solution here. Get two sets of batteries. When both sets are discharged, you can recharge both sets (4 and then 2). Most cheap chargers for nickel-cadmium or nickel metal hydride batteries just use current limiting, ie, a simple resistor in series with a voltage source, to keep the current below the safe limit for the battery. For AAA's that would be about 50 milliamps per cell. Usually the cells are in series, so simply removing a battery and shorting the connectors would increase the current above safe levels. For instance, to charge three AAA nicad cells in series from a 12 V source, the total voltage drop between source and batteries is 12 V - (3 x 1.4 V) = 7.8 V. To limit the current to safe levels, you need a resistor of 7.8/.05 = 156 ohms and 1/2 watt. Combining charged and discharged batteries in the same charger can result in a 'reverse-polarity' fault, where one of the batteries will be destroyed by the others. It may even burst. Rechargeable alkalines and lithium ion batties need more complex chargers. Dangerous Bill
  5. Years ago, someone made glasses that inverted the scene before them. Test subjects wearing the glasses therefore saw everything upside down. But after a couple of weeks, they adjusted and started to perceive everything upright. When the glasses were removed, they had to re-adapt all over again. These experiments were described in Scientific American maybe 20 yr ago. They illustrate the brain's ability to adapt, as well as its ability to fill in information that isn't even there. Dangerous Bill
  6. The whole concept of stewardship of the earth didn't really get going until the 1960's. I'm sure that in a desperate battle for the future of civilization, Shamu was probably the last thing on anyone's mind. More likely, it was, "Will I get my ass blown off in the next 24 hours?" While I was in the Canadian Navy reserve, we dumped our garbage straight in the ocean, which one sailor called, "The world's biggest garbage dump." Barely a day passed without encountering a dozen or so plastic bottles, steel barrels, pieces of lumber, oil slicks, etc. And this was 1962. Dangerous Bill
  7. Pb+2 (aq) --> Pb(OH)2 (s) (precipitates) --> Pb(OH)4 -2 (aq) (redissolves) Pb+2 (aq) --> Pb(OH)4 -2 (aq) (forms complex with only transient precipitate) Dangerous Bill
  8. The precipitate loses CO2, and the Al(OH)3 begins to lose water, forming polymers of aluminum oxide in a meshwork molecular structure, until in the limit, only Al2O3 would be left. It won't go all the way to alumina unless the water is removed by filtering and heating. Dangerous Bill
  9. It would work if he were a robot. My rheumatologist once told me that there were only two effective treatments for arthritis (as opposed to arthritic pain). Neither are FDA approved, perhaps because the drug companies don't make any money from them. 1. Chondroitin-glucosamine or just glucosamine. Take it every day. You won't see results for 2 or 3 months. 2. Move to Arizona. I did both. They worked. I walk 25 miles a week and can type -- well, like I'm typing now. Dangerous Bill
  10. The right answer to this will come from the medical schools you are planning to attend. Since recruiting the best students is an all-important task at these schools, they have people whose whole job it is to give advice on questions like these. Dangerous Bill
  11. ...are purported to be different. http://www.msnbc.msn.com/id/6448213/did/11009379/ Worse, Republicans thinking of GWB and Democrats thinking of, say, Hillary Clinton, have brain scans similar to drug addicts getting their rush. Anybody looked at this with a critical eye? Dangerous Bill
  12. I haven't text-messaged, but I've been infected by the Melissa worm a couple of times, and my brain is full of spyware. Dangerous Bill
  13. This proves that the Martians are real, and they come from California. Dangerous Bill
  14. Different? Shave a chimp and you've got us. Chop up some blood cells and the hemoglobin molecules are different only in unimportant details. In fact, every vertebrate animal has similar hemoglobin. Same for all our other parts. Man is only different because he kills other men over stupid ideas, not worthwhile goals like sex and food. Dangerous Bill
  15. I can't think of any text that handles both these subjects well. Two texts might do a better job. I like Electrochemistry for Chemists. Skoog's advanced text does spectroscopy fairly well. Dangerous Bill
  16. Even if you have 20 foot arms, you can still blow your hands off. I recall a friend of a friend who mixed KNO3, sulfur, and carbon, but it wouldn't ignite. He decided the crystals of saltpeter were too large. So he put the mixture in a bowl and started grinding it. You can guess the rest. He lost three fingers and his glasses (which kept him from being blinded). Chemistry is dangerous for two reasons: 1. You might maim or kill yourself. 2. You might get interested in it, go to school and become a professional chemist, and spend the rest of your life trying to find a job. Be a politician. Then you won't have to work and you'll never be short of cash. And you can spout the looniest crap and people will memorize and quote your very words. The crazier you get, the more they will love you. Dangerous Bill Retired chemist.
  17. It's not a completely outrageous idea. If air is trapped in chambers in the shoe, it will be warmed by compression, the way a bicycle pump barrel heats up when you pump up a tire. The air will cool again when it's released or decompressed. That's how air conditioners work. If you could figure out a way to compress the air in part of the shoe and released in some other part, ie, inside the shoe, it might provide some cooling. The moving air by itself would provide some cooling, too. A 20 degree difference would be a reach, but a lot less cooling would provide a lot of comfort. Headline: "Boy's 'Kool Shooz' Invention Causes Frostbite in Sonora Desert Hikers". Dangerous Bill
  18. I think it's 'cuz we don't have to draw predators away from the nest. Instead the female has to come up with ways to keep the male at home (or conversely, attract the male away from another home). Nature is a bitch. Dangerous Bill (on the other hand, the phenomenon of men dressing up in feathers and colored paint is or was found in lots of civilizations)
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