15.1 Energy and it’s forms Work = force x distance Work = transfer of energy Kinetic Energy= KE= ½ mv 2 Mass in kilograms, velocity in meters/sec Kg m 2 /s 2 we call a joule Pg 448 problems 1-3

15.1 Energy and it’s forms Gravitational Potential energy = PE PE= mgh sometimes called energy of position Elastic potential- like a rubber band or ball Why doesn’t a ball bounce as high as you drop it from?

Forms 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 Energy Chemical energy – energy stored in the bonds between atoms of a compound Gasoline has stored chemical energy Takes energy to rip bonds apart, energy is given off when bonds are formed

Forms 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 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= mc2 Page 452, questions 4,5,6,7

15.2 energy conversion Law of Conservation of Energy Energy 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 Conversion Example of a Pendulum PE is converted to KE, then back to PE Why does it slow down? Where does the energy go? Ans. To heat the air and the pendulum thru friction

Energy Flow diagram Example of an electric drill Energy in- electrical thru the cord Energy 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 out 200 J of work in 120/200 = 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 Resources Nonrenewable Source that we would use faster than they can be replaced Fossil fuels (oil, coal, natural gas) Uranium How about wood?

Renewable sources Hydroelectric Uses potential energy of rivers, or tides and waves to spin generators Solar Can 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 electrical Wind- used to convert KE (caused by thermal) to mechanical, then to electric Biomass- radiant to chemical to thermal, and maybe to mechanical to electrical Hydrogen fuel cell- chemical to electrical