15.1 Energy and it`s forms
Download
Report
Transcript 15.1 Energy and it`s forms
15.1 Energy and it’s forms
Work = force x distance
Work = transfer of energy
Kinetic Energy= KE= ½ mv2
Mass in kilograms, velocity in meters/sec
Kg m2/s2 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.
Mechanical (120 J)
Electric
in
Heat (45 J)
(200 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