15.1 energy and it’s forms work = force x distance work = transfer of energy kinetic energy= ke=...
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15.1 Energy and it’s forms15.1 Energy and it’s forms
Work = force x distanceWork = transfer of energyKinetic Energy= KE= ½ mv2
Mass in kilograms, velocity in meters/secKg m2/s2 we call a joulePg 448 problems 1-3
15.1 Energy and it’s forms15.1 Energy and it’s forms
Gravitational Potential energy = PEPE= mgh sometimes called energy of
positionElastic potential- like a rubber band or ballWhy doesn’t a ball bounce as high as you
drop it from?
Forms of EnergyForms of Energy
Mechanical =Sum of KE and PE on large scale
Thermal = sum of KE &PE on microscopic scale
As atoms move and bounce into each other more, their thermal energy increases
Thermal (heat) and temperature are related
Forms of EnergyForms of Energy
Chemical energy – energy stored in the bonds between atoms of a compound
Gasoline has stored chemical energyTakes energy to rip bonds apart, energy is
given off when bonds are formed
Forms of EnergyForms of Energy
Electrical- electricity is the movement of electrons
These charged particle can produce a force on other particles to cause work to be done
Electromagnetic- normally we think of this as radiation. Examples- light, X-ray, IR, UV
Sound Energy
Forms of EnergyForms of Energy
Nuclear Energy – energy stored within the atom.
The forces that hold an atom together and the actual conversion of small amounts of mass into great quantities of energy
E= mc2Page 452, questions 4,5,6,7
15.2 energy conversion15.2 energy conversion
Law of Conservation of EnergyEnergy cannot be created or destroyed, it
can only be converted from one form to another.
Does not include nuclear reactions where matter is converted to energy, but the total mass and energy in the universe stays the same.
Energy ConversionEnergy Conversion
Example of a PendulumPE is converted to KE, then back to PEWhy does it slow down?Where does the energy go?
Ans. To heat the air and the pendulum thru friction
Energy Flow diagramEnergy Flow diagram
Example of an electric drillEnergy in- electrical thru the cordEnergy out- mechanical to turn drill bit,
sound, heat
Efficiency –comparing the wanted energy coming out to the total energy going in.
Electric in
(200 J)
Mechanical (120 J)
Heat (45 J)
Sound (35 J)
Efficiency ?
Efficiency = work out over work in (or the usable energy out divided by the total energy put in)
120 J of work out200 J of work in120/200 = 0.60 or 60% efficient
Flow diagram for a light bulb?
Flow diagram for a car engine ?(car engines are only up to 30% efficient)
15.3 Resources15.3 Resources
NonrenewableSource that we would use faster than they
can be replacedFossil fuels (oil, coal, natural gas)UraniumHow about wood?
Renewable sourcesRenewable sources
HydroelectricUses potential energy of rivers, or tides and
waves to spin generatorsSolarCan be either to convert to thermal energy
or to convert to electric. (thermal more efficient)
Geothermal- can be used to collect thermal, Can also be used to convert thermal into
mechanical, into electricalWind- used to convert KE (caused by
thermal) to mechanical, then to electricBiomass- radiant to chemical to thermal,
and maybe to mechanical to electricalHydrogen fuel cell- chemical to electrical