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Physics for Future Presidents Notes-Final Exam

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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= …show more content…

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.. temp 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. b/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

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