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