(It's getting distinctly toasty here in Utah, which suggested the questions below.) 1) So the Uranium in the ocean is enough to warm it up, but not to boil it. Suppose we also used the Deuterium, supposing fusion worked. Would that be enough? 2) You can't boil the ocean by raising it to 212F. First, you need another 540 calories/gram to convert to vapor. And second, after you've boiled a little bit of ocean, atmospheric pressure rises and you have to get the temperature higher to boil the next bit. (Atmospheric pressure is about 30 feet of water, so boiling the top 30 feet of ocean would double the pressure.) Is there some convergence, or would some critical point phenomenon set in as heat is added? Rich -----Original Message----- From: math-fun-bounces+rschroe=sandia.gov@mailman.xmission.com on behalf of Eugene Salamin Sent: Mon 7/17/2006 1:46 PM To: math-fun Subject: Re: [math-fun] Another physics question --- Jason Holt <jason@lunkwill.org> wrote:
I also had a physics question recently. I was trying to explain e=mc^2 to my family, and was going to try to give an intuitive example of just how much energy there is in 300,000,000^2 kg*m^2/s^2.
Here is one illustration. Ocean water contains about 3 micrograms per liter of dissolved uranium. Extract the uranium from a volume of ocean, and fission all of it (using a breeder reactor), yielding about 200 MeV per atom. Use the released energy to heat that same volume of water. Water has a specific heat of 4800 J K^(-1) kg^(-1). What is the temperature rise? Answer: about 110 deg F.
I realized that impulse (or momentum), measured in kg*m/s, is much easier for me to conceptualize and explain: a baseball travelling at 30mph has a certain amount of kinetic energy that anyone can experience personally just by catching it. It was much more awkward to try to explain pushing a 1kg weight exactly hard enough to
accelerate it 1m/s^2, but only until it had travelled 1m. So if both units can be used to express energy, why do we speak of impulse as so different from energy,
Because energy and momentum are different physical quantities.
and is there an intuitive way to explain the conversion from the 30mph baseball's energy into kg*m^2/s^2 without calculus?
Perhaps, think of measuring the energy calorimetrically, by converting the energy into heat. Let a tank of water bring the baseball to a stop, and measure the temperature rise. This doesn't explain what energy actually IS; I can't think of a simple answer to that question.
I still remember the test question in 10th grade physical science in which I was asked to calculate the work required to carry a 10kg weight across a 10m room. I argued that, at least in the ideal sense, it required no work (if you're infinitely patient), since there was no change in gravitaional
potential energy, but the teacher wouldn't budge. I suppose I've resented work ever since.
This is one more example of how incompetent teachers drive students away from the phyical sciences. Was this public school?
Oh yeah, and maybe Mike Stay could also briefly summarize quantum gravity for us in a way that makes it clear just how that principle works. I was
wondering about that, too.
Yeah Mike, do that, would you please? Gene __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun