Physics for Future Presidents Notes-Final Exam

Energy: the ability to do work. Work= force x displacement. Power=energy/time Power is measured in watts or horsepower. Joules/sec=watts 1hp=746w=1kw Basal metabolic rate 2000kcal/day= 100w Batteries store energy in chemical form. They release energy by pumping electrons’ through wires from the minus pole to the plus pole. Devices inbetween convert this energy to another form, Efficieny- e. motor=85%, combustion= 20% Hydrogen is not a source of energy but a means of transportation Types of energy: kinetic e(in joules)= . 5mv^2.Solar energy- 1gw per km^2 Solar energy can be turned into electricity through solar cells 15%=cheap, 40% efficiency=expensive. Caloric theory of heat=caloric fluid flows from hot object to cold. Heat engine= device to turn heat energy into useful work: heat comes from something hot but only some goes to useful work. Satellites=free fall. Ionizing radiation=energy in the form of waves or paricle Beta radiation-just an electron, wont go through skin but r eally bad inside you alpha- he2+ nucleus-wont go through skin but bad once inside. Comes from radioactive particles like lead 210 or iodine. amma- high energy photon, may go through you. neutrineos-noninteracting, come from fusion, cosmic rays-very powerful. Come from supernovas. Moves at speed of light moderator-slows neutrons b/c they are absorbed better when slow ciritical mass needed for nuclear bomb-5kg, resistence of wire depends on length, longer=more resistance. Thickness-thinner=bigger resistance, material. Escape velocity=velocity required on the surface to completely leave a planet Rcket-goes nowhere near escape velocity – drag from atmosphere is bad, goes slower but carries fuel Tin Celsius = Tin Fahrenheit ? 2 ? 5 9 Tin Fahrenheit = Tin Celsius ? 9 + 32 . 5 Nuclear energy Source of energy of energy in plants=radioactive particles such as uranium and plutonium. A chain reaction is the doubling law that takes you from small numbers to high numbers in a small number of generations. Aromic bombs are based on chain reactions of u-235 or pu-239. Plutonium is manufactured in nuclear reactors. Difficult bomb design (implosion). Hydrogen bomb=fission ignites secondary reaction that contains two isotopes of hydrogen-most dangerous part of residual radioactivity.Nuclear reactors are based the chain reaction but normally work with neutron multiplication of 1 o reaction doesn’t grow. Moderators slow neutrons so they are more likely to attract to nucleus. If moderator is lost the chain reaction stops. If it runs away and c. r. begins to grow exponentially, the slowness of the neutrons limits the size of the explosion. Since a c. r. depends on slow neutronsa cr that depends on slow neutrons cannot give rise to a nuclear explosion so therefore a reactor cannot blow up like a bomb b/c when temp increases, aroms are moving too fast for the neutrons to hit them so the c. stops. It will blow up like tnt, but 1 mil times smaller than a bomb. N reactor= d evice in which sustained c. r. takes place. Neutrons hit nucleus to cause another fusion. Power doesn’t grow, is constant. Power comes out in the form of hear. Nuclear reactors use moderators- a chemical mixed with fuel that slows down the neutrons. Isotopes are different types of atoms (nuclides) of the same chemical element, each having a different number of neutrons. Power-rate of energy release. Cookies=high energy. Tnt=high power. I kg h=1 gal gas.Heat energy (or just heat) is a form of energy which transfers among particles in a substance (or system) by means of kinetic energy of those particle. Nuclear energy= energy stored between the forces between parts of atomic nucleus. Energy=measured in calories or joules. I watt-I joule/sec. most useful kinds of energy=chemical and potential. One calor is the enrgy it takes to raise one kg of water by one degree Celsius. 4k joules=calories. Solar cells- crystals that convert sunlight directly into electricity. K energy depends on sq of v. double speed=kinetic energy increased by factor of 4.. emp is a measure of hidden kinetic energy. Disorider= entropy. Double abs temp=double pressure. Heat engine= any engine that runs by turning heat into mechanic motion. Laws: 0-objects in contact tend to reach same temp. 1- energy is conserved. 2-you can’t extract heat energy w/o temp difference- tend towards same temp 3-nothng can reach temp of abs 0. Satellite in low earth orbit=5 mi/sec. high sat=slow. Geosynchrous sat= sat that orbites in 24 hours. . blackhole=escape velocity = faster than speed of light. Big mass or lots packed into small radius . rockets fly by pushing burned fuel down. /c rocket weighs so much more fuel, the amount of velocity gained by rocket is much less than the fuel velocity so very inefficient. Gravity=attraction between two masses. Radioactivity= explosion of nucleus atom. Radiation=pieces thrown out in explosion.. chernyobyl-vessel explosded in Ukraine, radiation went all the way to stockhom. Don’t know if deaths were from radiation or regular cancer. Firefighters died from radiation45 rem receved average.. 25 rem=1% cancer chance. The hydrogen economy is a proposed system of delivering energy using hydrogen.Thinks methane is the way since ch4. he term â€Å"hydrogen economy† describes an envisioned large-scale scheme of delivering energy by means of hydrogen, particularly for â€Å"motive power† (personal cars, buses, planes, ships, etc. ). This is attractive for several reasons, among them the clean way in which hydrogen burns (it only leaves water as a residue), its high energy per weight, and the fact that fuel cells can convert hydrogen’s energy directly into electricity that subsequently powers an electric motor, with a combined efficiency exceeding that of ordinary combustion engines.Around 4:00 am on the morning of March 28, 1979, water pumps in the non-nuclear section of Three Mile Islands’ Unit 2 nuclear power pla nt stopped working. This prevented the steam generators from removing heat from the plant and initiated an automatic shutdown of the reactor. The possiblity that the melting of fuel rods could result in a release of radioactivity to the surroundings was of great concern. The Nuclear Regulatory Commission was alerted at 8:00 am and the White House was alerted at 9:15 am. By 11:00 am, all non-essential personnel were evacuated from the facility.The remaining personnel worked to bring the situation under control over the next several days. According to the U. S. Nuclear Regulatory Commission, this accident, â€Å"was the most serious in U. S. com- mercial power plant operating history, even though it led to no deaths or injuries to plant workers or members of the nearby community. But it brought sweeping changes involving emergency response plan- ning, reactor operator training, human factors engineering, radiation protection, and many other areas of nuclear power plant operations. â €  – melted cre