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Energy. Energy. The ability to do work. Work : a transfer of energy. Both energy and work are measured in Joules J Energy and work are related. When work is done on an object energy is being transferred to the object. Law of Conservation of Energy.
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Energy • The ability to do work. • Work : a transfer of energy. • Both energy and work are measured in Joules J • Energy and work are related. When work is done on an object energy is being transferred to the object.
Law of Conservation of Energy • Energy can not be created nor destroyed only changed to a new form. • Basically means in a closed system that amount of energy going in will equal the amount of energy coming out. • In some situations energy may be lost due to friction forces and changed to heat.
Energy and Mass • Albert Einstein Theory of Relativity 1955 • E = MC² c= speed of light 3.0 x 10 ₈ m/s • Says as matter is destroyed energy is released and matter can be created from energy. • The law was latter modified the law of conservation of energy to include mass.
Energy Conversions • Energy can be converted from one form to another. Conversions are constantly occurring.
Types of Energy • There are many forms of energy either renewable or non-renewable.
Types of Energy • 1. Mechanical (kinetic or Potential) • 2. Thermal/Heat • 3. Chemical • 4.Electromagnetic • 5. Nuclear • 6. Electrical
Mechanical Energy • Energy associated from motion and position of everyday objects. • ME = KE + PE
Kinetic Energy • Energy of motion. • KE = ½ MV² • Doubling mass = doubling KE • Doubling velocity = quadrupling KE
Potential Energy • Energy stored as position, shape, or condition. • Cello bow & arrow food fuel glycogen • Two types: • 1. gravitational potential energy: based on height & mass GPE = mgh m: mass g: acceleration due gravity h: height m : kg g = 9.8 m/s² Earth ht : m To convert from mass to weight multiply by 9.8 Mass x 9.8 = Weight (N)
2. elastic: based on condition/elasticity. • The potential energy of an object that is stretched or compressed. • Can spring back to its original shape after being compressed or stretched.
Most common is GPE to KE • Changes from GPE to KE can go in both directions. • Gulls use GPE to break open oyster shells.
Pendulums • Some of our first clocks relied on pendulums that swung to keep time. It converted pe to ke. • Pole vaults, roller coasters, skiing
Thermal Energy When atoms move faster the Thermal Energy will increase and the object will become warmer.
Thermal Energy • Total P.E. + K.E. • depends on mass and temperature • Teapot vs. cup = teapot has more due to mass of particles • Hot tea vs. Cold tea = hot has more due to more K.E.
Heat (4T’s) • Transfer of Thermal Energy from one object to another because of temperature differences. • Always moves from Hot to Cold
Temperature (4E’s) • How hot or cold an object is • Related to the average K.E. of particles in an object • Due to their random motion
Specific Heat • The amount of heat required in calories to raise the temperature of 1 g. by 1ͦͦ c
Specific Heat • Like iron, most substances have a specific heat lower than that of water, meaning that less heat is needed to raise their temperature than is needed to raise the temperature of water by the same amount. Most liquids have a specific heat less than half that of water and, in general, the specific heat of solids is lower than that of liquids.
Thermal Expansion • An increase in volume of a material due to an increase in temperature . • Particles move farther apart as temperature increases • Gases expand the most
Calorimeter • Used to measure changes in thermal energy.
Conduction • Transfer of T.E. with no overall transfer of matter. • Particles are touching. • Faster in solids than gases because collisions are less. • Metals (conductors) conduct T.E. fast due to movement of molecules which is more free.
Conductors • Any material that easily transfers thermal energy. • Best are metals such as gold and copper.
Insulators • A material that conducts T.E. poorly. • Wood, plastic , rubber, air , foam cups • Wood heats slowly due to being a poor conductor of T.E. • Air is used in double pane windows and wool clothes as insulators.
Convection • Transfer of T.E. when particles move from one place to another. Due to density and temperature. • Convection currents occur when a fluid circulates in a loop as it alternates form heating up to cooling down. • Examples: ocean current, weather systems, rocks
Radiation • Transfer of Energy by waves moving through space. • Heat lamps , microwaves, sun
Chemical Energy • The energy stored in chemical bonds. • When bonds are broken, the released energy can do work. • Wood is burned and energy is released as heat. • Examples: fuel , coal, gas
Electromagnetic Energy • Energy transferred through space in waves. • Examples: visible light, x-rays, gamma rays, radio waves.
Nuclear Energy The energy stored in atomic nuclei. Nuclear power plant uses fission reactions by splitting nuclei apart. This process releases energy. Nuclear fusion releases energy when less massive nuclei combine to form a more massive nucleus.
