energy and its forms (15.1). energy : the ability to do work work: the transfer of energy - energy...

ENERGY and its FORMS (15.1)

energy : the ability to do work

work: the transfer of energy

- energy is transferred by a force moving an object through a distance…

both are measured in joules (J)1J = 1N-m (newton-meter)

kinetic energy: energy of motion

the kinetic energy of any moving object depends on mass and speed

kinetic energyKE = 1/2mv2

potential energy: energy that is stored as a result of position or shapeenergy with the potential to do work

gravitational potential energy: potential energy that depends on an object’s height

an objects gravitational potential energydepends on its mass, height and the acceleration due to gravity

potential energy (PE) = mgh

elastic potential energy – the potential energy of an object that is stretched or compressed

Forms of Energy…

mechanical energy: energy associated with motion and the position of everyday objects

thermal energy: the total potential and kinetic energy of all the microscopic particles in an object

chemical energy: the energy stored in chemical bonds in compounds

electrical energy: energy associated with electric charges

electromagnetic energy: form of energy that travels through space in the form of waves

nuclear energy: energy stored in atomic nuclei

the nucleus of an atom is held together by strong and weak nuclear forces which can store an enormous amount of energy

Chapter 15.2Energy Conversion and Conservation

energy conversion: energy can be converted from one form to another

law of conservation of energy states that energy cannot be created or destroyed – it converted from one form to another

the gravitational potential

energy of an object is converted to

the kinetic energy of motion as the

object falls (avalanche)

Energy Calculations

• when friction is small enough to be ignored, and no mechanical energy is added to the system, then the system’s mechanical energy does not change

• mechanical energy = KE + PE

conservation of mechanical energy

(KE + PE) beginning = (KE + PE) end

Energy and Mass

in Einstein’s equation (E=mc2 ) – energy and mass are equivalent and can be converted into each otherE (energy) = m(mass) x c (speed of light)2

- energy released as matter is destroyed and matter can be created from energy

Chapter 15.3ENERGY RESOURCES non-renewable energy sourcesexist in limited quantities – once used, cannot be replenished…oil, natural gas, coal and uranium

fossil fuels (oil, natural gas and coal) – formed underground from the remains of once-living organisms – account for the majority of the world’s energy – not evenly distributed throughout the world

renewable energy sources can be replaced in a relatively short period of time – most originate directly / indirectly from the sun –

hydroelectric, solar, geothermal, wind, biomass, nuclear fusion

Conserving energy resources…

energy resources can be conserved by reducing energy needs and by increasing the efficiency of energy use

energy conservation: finding ways to use less energy or to use energy more efficiently