GEO 301 Lecture Notes - Lecture 11: E-Commerce, Ebay, Convenience Store

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emeralddonkey1

17 Sep 2012

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Several levels of e-commerce involvement: ranging from informational to transactional. Different types of players in the internet channel: hardware: isps, telecoms, etc. Intermediaries: generate revenue through advertising, subscriptions, and commissions. In the beginning, e-commerce was characterized by vast numbers of upstarts, most of which failed. Over time, it has stabilized, with large players with the best business models (amazon, e-bay) dominating the market. Customers are less likely to purchase complex products (cars, financial services, etc. ) over the internet. Customers are more adverse to committing to high-price transactions over the internet (cars, electronics) People are more likely to want to purchase enjoyable products (cars, clothing, etc. ) in person. People are more likely to purchase un-leisurely products (rental insurance) remotely. Factors in e-commerce: complexity of the product and transaction. More likely to purchase simple products (books, transportation: price. Two more locations in downtown coin the city that he wants to open up. Customer profile more specialized and looking at specific people.

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A nuclear reaction is represented by an equation similar to theequation for a chemical reaction. An example of a nuclear reactionis the decay of radium into radon by the emission of an alphaparticle (a helium nucleus). The equation for this reactionis

^{226}_{\ 88}{\rm Ra}\; \rightarrow \, ^{222}_{\ 86}{\rmRn}+\;^4_2{\rm He}.

The superscript preceding each element indicates the nucleon numberof that particular nucleus (total number of protons and neutrons).The subscript indicates the charge of the nucleus, which is equalto the atomic number for nuclei. Nuclear reactions frequentlyinvolve electrons (sometimes called beta rays) and photons(sometimes called gamma rays). Electrons, which have nucleon number0 and charge -1, are represented in equations as either ^{\ \;0}_{-1}\beta or ^{\ \; 0}_{-1}{\rm e}. Photons are represented as^{0}_{0}\gamma to emphasize that they have no nucleon number andcarry no charge.

In nuclear reactions, several conservation laws are usuallysufficient to determine the products or reactants. One of these isconservation of nucleon number. The total number of neutrons andprotons in all of the reactants must be the same as the totalnumber of protons and neutrons in the products. Although protonsand neutrons sometimes change into one another, neither can simplydisappear. Another important conservation law is conservation ofcharge. The net charge of the reactants must be the same as that ofthe products.

Notice that, in our equation for the decay of radium, the sum ofthe nucleon numbers on each side is 226 and the sum of the chargeson each side is 88. If you knew everything in this equation exceptthe isotope of radon produced, you could simply subtract 4 from 226to find the nucleon number required to make the nucleon number ofthe products equal the nucleon number of the reactants. Similarly,if you knew everything in this equation except for the identity ofthe product element, you could simply subtract 2 from 88 and thenlook in a periodic table to find that the element with atomicnumber 86 is radon.

In parts A and B consider the decay of radon by alpha particleemission:

^{222}_{\ 86}{\rm Rn}\;\rightarrow\;X +\,^{4}_{2}{\rm He}.

a. What is the nucleon number of the element X?
Express your answer as an integer.

b. What is the atomic number (nuclear charge) of the elementX?
Express your answer as an integer.

n parts C and D consider the decay of Potassium-43 into calcium-43via the following reaction:

^{43}_{19}{\rm K} \rightarrow ^{43}_{20}{\rm Ca}+\,X.

c. What is the charge of the emitted particle X?
d. is not visible yet

E. An isotope of potassium with a half-life of roughly one billionyears is often used in radioactive dating. This isotope decaysthrough electron capture, the process of drawing an electron intothe nucleus. What is the chemical symbol for the element thatresults from this process? The equation for the reaction is

^{40}_{19}{\rm K}+\,^{\ \;0}_{-1}{\rm e}\rightarrow \,?.
Express your answer as a chemical symbol (e.g., Na forsodium).

f. The reaction energy of a reaction is the amount of energyreleased by the reaction. It is found by determining the differencein mass between the reactants and products and then using E=mc^2 toconvert the lost mass into the released energy.

Look again at the equation for the decay of radium (Ra), given inthe introduction. Use the following table of masses to determinethe reaction energy of this reaction.
Nucleus or particle Mass in atomic mass units
radium-226 226.025402
radon-222 222.017571
alpha particle 4.002602
Express your answer in joules to three significant figures.

please answer fully... thank you

An important question to consider when thinking about globalwarming is, "If the ice sheets near the poles melt, how much willthe sea level rise?" This seems like a difficult question, giventhe odd shapes of both the ice sheets and the oceans. But there aresome accurate approximations that allow the answer to be estimatedfairly accurately with reasonably simple calculations.

The critical idea is that both the thickness of the ice sheets andthe amounts of the sea-level rise are extremely small compared tothe radius of the earth. The radius of the earth is about 2/p x 107m -- more than 6000 kilometers. The ice sheet thicknesses we willbe concerned with are single digit miles and the sea level riseswill be in dozens of feet. As a result, in thinking about them, wecan essentially ignore the curvature of the earth. We can imaginepeeling the map of the earth off a globe and flattening it out (bymaking cuts, not by stretching it, so that we preserve the area).Then, both the ice and the sea level rise can be treated as right(not tilted) cylinders (though with funny shaped bases and tops).Since we know that the volume of a right cylinder is the area ofthe base times the height, we can easily estimate all the volumeswe need. A schematic picture of this approximation (with the heightof the ice mass greatly exaggerated -- you couldn't see it if Ididn't) is shown below. The error in these approximations is on theorder of the height of the cylinder considered divided by theradius of the earth; a very small number.
a. Assume that (after flattening the surface of the earth in ourimaginations) the ice sheet to be considered covers an area, A, andhas a thickness, d. The oceans currently cover about 75% of theearth's surface, and note that the surface area of a sphere is 4pr2where r is the radius of the sphere.

Generate an equation that will allow you to calculate h, the heightthe ocean levels will rise due to the melting of a an ice sheet interms of A, d, and r

b. As shown in the combined satellite photo on the right (fromGoogle Earth), Greenland is covered by a sheet of ice. This ice hasbeen measured to have a mean thickness of about 2 km. Recentobservations indicate that this ice sheet is beginning to retreat-- that it is melting at an accelerating rate.

Using the depth of the ice sheet and the scale given on thepicture, estimate how much sea level rise would be produced by themelting of the entire ice sheet lying on Greenland. (Note: You caneasily look this information up on the web. But the goal of thisproblem is in part to develop your estimation skills for thepurpose of building your ability to decide for yourself whether anygiven piece of information you find on the web is reasonable orbogus.)

19. The interstellar medium has a cool component measuredvia_________ observations and a hot component revealed by________observations.
AX-ray; optical
BX-ray; infrared
CX-ray;gamma-ray
Doptical; X-ray
Einfrared; X-ray

20. Which of the following processes will NOT cause a gas cloudtocollapse?
Aionization from youngstars
Bsupernovaexplosions
Cgalacticrotation
Dthe expansion of theUniverse

21. What is responsible for emitting photons in anemissionnebula?
Aexcitedprotons
Bexcitedneutrons
Cexcitedelectrons
Dexcitedneutrinos
Eexcitedastronomers

22. White dwarf stars are supported from collapse by
Anuclear fusionreactions in a shell around the core.
Belectron degeneracypressure.
Cnuclear fusion reactionsin their cores.
Dcentrifugal force due torapid rotation.

23. The "star" that is seen at the center of a planetarynebulais
Aa planet in theprocess of formation.
Ba small, hot, and verydense, white dwarf star.
Cthe accretion disk arounda black hole.
Dcomposed almost entirelyof neutrons, and is spinning rapidly.

24. A white dwarf star, the surviving core of a low-massstartowards the end of its life, can be found ontheHertzsprung-Russell diagram
Aat the bottom end ofthe main sequence, along which it has evolvedthroughout itslife.
Babove and to the right ofthe main sequence, since it evolved thereafter itshydrogen-burning phase.
Cbelow and to the left ofthe main sequence.
Dat the upper left end ofthe main sequence, since its surfacetemperature is extremelyhigh.

25. The mechanism which gives rise to the phenomenon of thenovais
Amaterial fallinginto a black hole and being condensed to the pointwhere athermonuclear explosion is produced.
Bthe impact and subsequentexplosion of a large comet nucleus upon astar's surface.
Cthe completedisintegration of a massive star because ofthermonuclear runawayin the star's interior.
Dmatter from a companionstar falling onto a white dwarf in a closebinary system,eventually causing a nuclear explosion on thedwarf'ssurface.

GEO 301 Lecture Notes - Lecture 11: E-Commerce, Ebay, Convenience Store

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