wpenrose

Here's a puzzler for you. ...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?

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

....But what i am most curious about at this point is that, how would you go about generating electricity from gravity?

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

Sorry if this has already been posted, but this has been bugging me for a while and a search didn't turn up anything. We keep talking about alternative energy sources everywhere when there is a constant energy around us all the time. What I want to know is, could gravity be used as a feasible source of energy?

Yes. It's called hydroelectric power.

Dangerous Bill

I have an appliance that uses 3 AAA batteries, and I have a charger that can only charge 2 or 4 AAA batteries at a time. I need a way of charging all 3 batteries at once using the charger, without overcharging or blowing something up...

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

Ok, imagine that we have glasses on say 5x magnification and everything we see is proportional to what we see. Now say we put on –5x glasses on and we see things smaller but they are all proportional. How do we know what we see is the actual size? Am I making sense here? Can anyone here understand what I am saying?

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

You know the big naval battles between germans and british and americans and japanese during WW2? I wonder, how big was the impact on the ocean environment? ships blowing tons of artillery straight to the water, massive sinking ships that must leak alot of petrol when they get hit and sunk by other ships artillery and also airplanes crashing into the water they too, leaking petrol. I have certainly not heard about it, but come to think of it it must have had a negative effect on the sea ecology, but how big?

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

Beat me too it... its very interesting just how effecient they are' date=' maybe small ones could be harnessed as an energy source some day...

[/quote']

 

They were on sale at Home Depot the other day, so I went and picked one up.

 

The clerk said, 'For God's sake, don't drop it!"

 

It's great. I fired Waste Management's weekly pickup. It takes cans, glass, pets, food, food wrappers, aluminum foil. You name it. It's gone and just a burst of hard x-rays to show for it.

 

Dangerous Bill

 

0.1M NaOH added dropwise to 10 drops of Pb(NO3)2

&

1 drop of 0.1M Pb(NO3)2 added to 10 drops of 0.1M NaOH

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

1) 2 Al 3+ + 3 CO3 2- -----> Al2(CO3)3 ( white ppt )

2) CO3 2- + 2H+ -----> CO2 (effervesence ) + H2O

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

I was reading the post on cracking knuckles and if it causes arthritis or not. I got to thinking about arthritis and remembered that I once knew a fellow that used WD-40 on his arthritic joints.

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

What physiologically happens to the body when it's exposed to a (lethal) overdose of these painkillers' date=' and what kinds of differences are there between the three when this happens?[/quote']

 

Aspirin causes acidosis. It lowers the blood pH. Only a fraction of a pH unit will bring you to grief. The only treatment is hemodialysis.

 

Acetaminophen (tylenol) trashes the liver, especially when taken with alcohol.

 

I don't know what ibuprofen does.

 

Dangerous Bill

What should I study to become a neurosurgeon, which subject in particular...What courses should I ask for.

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

...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

You think its true?

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

1. What voltage is actually required? (I think it was running at 3 volts when I last tried it).

 

2. A high current is clearly required here.

 

3. Would the sodium produced stick to the electrode' date=' or float to the top of the NaOH? If so would it catch fire?

 

4. At 100 amps, how long would it take to produce a gram of sodium?

 

FYI I tried to buy some from Aldrich Chemicals but they said no. And that was before the days of global terrorism.[/quote']

 

The voltage is immaterial, as long as it exceeds the reduction potential of sodium. The best bet is to put a low-value resistor in series with the electrolysis, and increase the voltage until the measured current is just less than the rating of the fuse or circuit breaker. The resistor (a light bulb will do) keeps the current in bounds.

 

As someone mentioned, the sodium will float, but it will be molten, too. You must have a dry, inert gas to blanket it, or you will have sodium oxide instead.

 

Chemical companies will not sell chemicals to private persons, mainly because of the civil liability, and only secondarily because of complications with the DEA and DHS. What that means, is that if Aldrich sells you some sodium and you blind or maim yourself, you'll have lawyers knocking at your door offering to sue the chemical supplier on your behalf.

 

1 amp flowing for one second is one coulomb, or 1/96500 of a mole, of electrons. To convert one gram of sodium ion to sodium metal, with an atomic weight of about 23, will take how many seconds at 100 amps?

 

I forget whether you can use carbon electrodes, or whether you end up with sodium carbide. Try to avoid using mercury if at all possible.

 

Dangerous Bill

In the lab I am a scientist' date=' but when I go for a walk in the woods, I am a creature.

Some might even say, a specimen.[/quote']

 

The local forest creatures may think of you as 'food'.

 

Dangerous Bill

This proves that the Martians are real, and they come from California.

Dangerous Bill

Man is different from other life on this planet, is it possible that man is only part from this planet??????

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

Unfortunately I have not seen very many scientists try to promote meaningful dialogue. So we are left with a battle of two idealogues' date=' one being the fundamentalist Christian, the other being the fundamentalist atheist scientist like Dawkins.

 

As a Christian I embrace evolution and percieve no threat, but then I have been educated and worked under rational professors who do not percieve religion to be the enemy. Many of these people are Christians themselves.

 

Im willing to admit the ignorance and wrong of many who claim to be Christians in propagating this stupid conflict.

[/quote']

 

In fact, many illustrious biologists have tried to provoke meaningful dialog about evolution, and this has always turned out to be their weakness. Standing in front of a crowd with a tray of fossils and a logical argument is not much help when the opposition asks if the people really want to risk their immortal souls over an 'unproven theory'.

 

It is true that many Christians can easily reconcile modern science with their religion. That's why I separate and characterize fundamentalists as a 'cult'.

 

I, too, am a Christian, and I accuse these people of hijacking my God and turning him into a vengeful bigot.

 

Dangerous Bill

Welcome fellow evolutionary biologists' date=' other biologists, other scientists, theologizes and of course other random people...

Comments appreciated[/quote']

 

Forget arguments from logic. Fundamentalist cults don't do logic. 'But God told me it's the other thing.' is all they need to know.

 

For illustration only:

Let's assume for the moment that you're not gay. (No offense to you personally.) Someone sits you in a classroom and forces you to read a gay porn novel, a really explicit one. It's enough to sicken you, even if you are philosophically tolerant towards gay folk.

 

That's how cultists feel when they have to open a biology textbook. To them, Darwin spits in the face of the version of God they've been taught about since infancy.

 

Don't worry, physics people. After evolution, there's the age of the universe and the obviously defective round earth theory. Also, political science folks, wars are blessed by God and the outcome decided by His intervention.

 

Get ready for the theocracy.

http://www.theocracywatch.org

http://www.theocracywatch.org/dominionism.htm

 

Dangerous Bill

That sounds pretty damn nasty' date=' gloves for me then!

 

[/quote']

 

Um, gloves are made from organic polymers. They will likely burn just like any other material. At least, you can't assume they won't.

 

Dangerous Bill

Hello. I'm looking for a instrumental analysis textbook on spectroscopy and electrochemistry. If anyone has any good recommendations please post them up. I have a number from Skoog and would like a few others.

 

Thank you for your efforts.

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

by the way bud, you can always be far enough away from a reaction to do it safely.

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.

This is a qusetion about pressure and diffusibility.

If i apply pressure on a shoe having a provision for inlet of air like in a nike air shoe only with hole spaces for air inlet(wearing it)and then relieve ...

I am sorry if it aint clear enough coz i am inexperienced in physics ie. 7th grade

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

If we look in nature usually the male is the more colorful or decorated of a species. But for humans, the female is more colorful and decorative. Both are connected to sexual attraction phenomena. Does anyone have an ideas of why the colorful lure switches for humans? It appears to show a cross sexual part of the brain being used for human animal sexuality.

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)