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Energy Chapter 15 What is energy? • Defined as the ability to do work or the ability to cause change. • Measured in joules. • Can occur in many forms. Kinetic Energy • Energy of motion • All moving objects possess kinetic energy • Can change from one type to another Factors which affect kinetic energy: • MASS •K.E = ½ • VELOCITY 2 mv Potential Energy • Energy stored in an object due to its position. • Examples: Gravitational potential energy • Dependant on the weight of the object and its height above some reference point. • Formula: Elastic Potential Energy • Potential energy due to to the physical distortion of an object. • Depends on: – Type of material – Amount of distortion Six main forms of energy: 1. Mechanical energy • Energy associated with motion: 2. Heat energy • Internal motion of particles of matter that often causes a change in temperature. 3. Chemical energy • Energy released or stored when atoms are bonded together. • Bonds can be broken to release this energy. 4. Electromagnetic energy • A form of energy that travels through space in the form of waves. 5. Nuclear energy • Found in the nucleus of the atom • Most concentrated form of energy • Reason for the brightness and heat of the sun • Nuclear link 6. Electrical energy • Energy associated with electrical charges or moving electrons. Energy conversions • All forms of energy can change from one form to another. • Examples: Conservation of Energy •Energy can be neither created nor destroyed. Calculations • When friction is absent or small enough to be ignored, total mechanical energy = KE + PE • Problems 1-3 page 458 Theory of Relativity • Developed by Albert Einstein in 1905. • Energy is directly related to mass. • E = mc2 Energy Resources • Nonrenewable: – Cannot be replaced after being used up. Examples: Renewable resources • Can be replaced in a relatively short period of time. Examples: • Hydroelectric • Solar • Wind • Biomass • Thermal Hydroelectric energy • Energy obtained by damming a river and controlling the flow. • Potential energy converted to kinetic converted to electric Solar energy • Using sunlight as an energy source on earth. • A huge amount of energy available, but problems include storage and dependence on climate. Wind power • Relatively unlimited amount of energy available. • Problem: What if it is not windy? Geothermal energy • Using the heat beneath the Earth’s surface. Hydrogen fuel cells and biomass • Hydrogen fuel cells: a way to generate electricity by reacting hydrogen with oxygen. • Biomass: using living organisms to produce energy. assignment • Page 469-470 • 1-10, 12, 13, 14, 18, 21, 23, 25, 27, 28, 29, 32