Chapter 3 Phys 100
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This 0 page Class Notes was uploaded by Rebeca Cotton-Baez on Monday November 2, 2015. The Class Notes belongs to Phys 100 at State University of New York at Potsdam taught by Dr. Lee in Spring 2015. Since its upload, it has received 14 views. For similar materials see Physical Science in Physics 2 at State University of New York at Potsdam.
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Date Created: 11/02/15
Chapter 3 Energy is transformed through working or heating the total amount remains constant 1 Work Workforce x distance Wfd Units WJoule FNewton Dmeter Work depends on force and the parallel distance through which the force acts 0 Units of work and energyJoule J 0 Force is parallel to distance and same directionwork is maximal F D Force perpendicular to distance work is zero F D W is not maximal if they39re not parallelsame direction 0 Zero distance0 work 0 Displacement perpendicular to applied force no work Force Walking this direction perpendicular no work 7 lclicker Question 1 B 300 N F 8 meters cicker Question 2C 300 Nx8 24x10quot3 Nm 2 Power 0 The rate at which work is done on the rate at which energy is transformed Pwt Power wt wattsjouestime 1 horse power746 watts 1 hp clicker question 6 B T 5 seconds Wmg W 245 kgx98 w245 N WFd 245x3 m W735 joules Pw 735 J5 seconds P147 W 0 Potential Energy 0 Energy associated with position 0 Gravitational potential energy gt Measuring h need measurement height 0 Also elastic springs and electric changes potential energy Lab notes The greater the height the more work Wmgh Transfers energy from weight to work Potential energy at any given height it39s ready to go into motion depends only on vertical height 0 Potential energy changes every time anything moves up and down 0 Potential energy is NOT conserved When the ball is at the bottom it always goes the same speed It is almost like the ball remembered where it had started Finish Start F through a little distanceopposing force Wdifference between potential energy at 1 height and another 3 Potential Energy Potential energy joules weight x height PEmgh Energy associated with position gravitational Above table positive potential energy On table 0 potential energy Below table Negative potential energy l clicker 8 C 4 Kinetic Energy 0 Energy associated with motion 0 Results from work or change in potential energy 0 Speed squared double speed KE increases by 4 KE12mass velocityquot212 mvquot2 lclicker question 9 B 5 Energy ow and energy form Energy ow Energy can do work as Work against inertia Work against gravity Work against friction Work against shape Combinations of any of the above Energy forms 0 Mechanical 0 Kinetic pluspotential energy Electrical energy 0 Charges current 0 Chemical Radiant Nuclear cicker 13 A kinetic energy cicker 14 B 6 Energy conversion and energy conservation 0 Any form of energy can be converted into another form 0 Energy ows from one form to another in natural processes 0 Example pendulum ependumum xed KEPE Ex Drop ball at rest velocity is 0 therefore kinetic energy is 0 PE is mphKE10 PE mgh Q Drop from rest Height O This position MEKEPE Final Vf O KEKE12m vquot2 Energy is never created or destroyed Energy can be converted from one another but the total energy remains constant 0 Eg freefall Energy transfer mechanisms work andor heat vr Zgh 35 Example Ball m1 Kg free fall 9E Potential energy mgh At 10 m Kinetic energy 12 m v quot2 Enerov sources todav Primarily wood to coal to petroleum with industrialization 89 can be traced to photosynthesis Uses 0 13 burned for heating 0 23 burned in engines Petroleum Oil from oil bearing rock Organic sediments transformed over time by bacteria pressure and temperature Natural gas formation similar except at generally higher temperatures Petroleum and natural gas usually found together Supplies are limited 25 from offshore wells over 50 imported m Accumuated plant materials processed over time by pressure and temperature Progression peat to lignite to subbituminous to bituminous lmpurities 0 Minerals lead to ash o Sulfur leads to sulfur dioxide gas pollutant Petroleum natural gas and coal fossil fuels Moving water 0 Renewable with rainfall Gravitational potential energy of water converted to electrical energy Hydroelectric plants generate 3 of US total energy consumption 0 Growth potential limited by decreasing availability of new sites Nuclear Based on nuclear ssion reactions of uranium and plutonium Water heated in reactor and then used to produce steam to turn generating turbines Safety of nuclear power generation is controversial Enerov Sources Tomorrow Alternative source of energy one that is different from these commonly used today Today fossil fuels nuclear falling water Tomorrow Solar geothermal hydrogen gas fusion Enerov conservation A way of reducing the need for additional energy Saves money for the consumer Can make demands easier to meet Energy ef ciency improvements also reduce the need for additional energy Much of the energy we consume is wasted individual and technological problem Solar Technolooies Solar cells 0 Direct conversion of light to electricity Power Tower 0 Mirrors focus on sunlight to heat water for steam generation Passive application 0 Designs to use solar energy ow naturally Active application 0 Solar collector used to heat water air or some liquid Agriculture and industrial heating 0 Direct use of sunlight to dry grain cure paint etc Wind energy o Turbines generate electricity 0 Wind often inconsistent Biomass 0 Plant material formed by photosynthesis o Burned directly or converted to thermal fuels 0 Ocean thermal energy conversion 0 Uses temperature difference surface and ocean depth to generate electricity Geothermal Enerov Hot dry rock 0 85 of total resource 0 Associated with volcanic activity Geopressurized resources 0 Underground reservoirs of hot water containing natural gass o 14 of available resources 0 Dry steam 0 Very rare only 3 sites in US 0 Hot water 0 Makes up most of the recoverable geothermal resources 0 Can be circulated directly into homes businesses farms and so on Hydrogen Energy storage and transport system 0 Must be generated for utilization 0 One possible source water H20 0 Clean 0 Combustion produces water 0 Possible problems 0 Best stored as liquid hydrogen cold 0 Extremely ammable Question 17 B petroleum 18 B used to produce electricity 20 E all of the above
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