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Transcript
Energy DEFINITION • the ability to cause a change • common measurement unit = Joule (J) FORMS • energy exists in many different forms: 1. 2. 3. 4. 5. 6. 7. 8. 9. potential kinetic mechanical heat chemical nuclear electrical light sound (Gravitational) Potential Energy • abbreviations: PE, GPE, and PEgravitational • energy stored in a non-moving object due to its position, shape, or composition in a gravitational field Kinetic Energy • abbreviation: KE • energy of motion • all moving objects have kinetic energy Mechanical Energy • total potential energy & kinetic energy of an object • ME = PE + KE Heat • Energy that moves from hot objects to cooler ones Chemical Energy • energy stored in chemical bonds Nuclear Energy • Energy stored in the nucleus of an atom Electrical Energy • Energy of moving electrons Light Energy • Energy contained in electromagnetic waves Sound Energy • Energy produced by vibrating objects Potential Energy Word Problems A 4 kg rock is sitting on a 3 m ledge. How much gravitational potential energy does it have? GIVENS: m = 4 kg h = 3 m g = 9.8m/s2 UNKNOWN: PE EQUATION: PE = mgh SUBSTITUTION: PE = (4 kg) x (9.8m/s2) x (3 m) SOLUTION: 117.6 J Kinetic Energy Word Problems A 3 kg ball is rolling at a velocity of 2 m/s. How much kinetic energy does it have? GIVENS: m = 3 kg v = 2 m/s UNKNOWN: KE EQUATION: KE = ½ mv2 SUBSTITUTION: KE = ½ (3kg)(2m/s)2 SOLUTION: 6kgm/s2 = 6 J LAW of CONSERVATION of ENERGY Energy cannot be created or destroyed, BUT it can be transferred from one object to another AND it can be changed, or converted, from one form to another Energy Transfer • Occurs when one object passes some of its energy to another object • First object loses energy; second object gains energy • 3 main ways: conduction, convection, and radiation Conduction • Energy is transferred within an object or between objects that are touching • As particles in objects collide, their energy is transferred Convection • Fluids (liquids & gases) transport energy from one place to another • Forms convection currents Radiation • transfer of energy through electromagnetic waves • radiation is felt as energy is absorbed by a material Energy Conversions • AKA energy transformations • Change of one form of energy into another example Electric Fan • Electrical → kinetic • When you plug in the fan, electricity causes the blades to move
