Download Energy Conservation - Miss Jones 8th Grade Science

Energy
Notes
Energy
Is the ability to do work (no energy = no
work)
 Unit for measurement is the joule (J)
 Energy has no direction

Forms of Energy
Mechanical Energy – made up of
potential and kinetic energy
 Example: Ball rolling down a ramp
 Potential Energy – energy of position or
stored energy (case of chemical bonds)
 Kinetic Energy – energy of motion

Potential Energy
Potential energy is energy waiting to be
released either due to position (boulder
on top of a hill) or chemical make up
(exothermic/endothermic bonds)
 Gravitational potential energy is based
on height (think roller coaster)

Gravitational Potential Energy
Eg = mgh
 E = Gravitational potential energy in
Joules
 m = mass in kilograms
 h = height in meters
 g = 9.8 N/kg or 9.8 m/s/s
 Eg = mgh is equal to Eg =
(weight)(height) since mg is = weight
 Weight is in newtons

Kinetic Energy
Energy of motion
 Ek = ½ mv2
 Ek = Kinetic energy in Joules
 m = mass in kilograms
 v = velocity in m/s

According to order of operations you
must square your velocity before
multiplying mass.
 Some people find it easier to think of the
equation as Ek = (mv2)/2

Other forms of energy
Thermal (heat) energy – internal motion
of atoms. The faster they move the
more energy they produce
 Chemical energy – chemical changes
that bond atoms together
(photosynthesis, cellular respiration and
fire)

Nuclear energy – nucleus undergoes
fusion or fission to release energy
 Electromagnetic energy – moving
electrical charges (light energy).
Examples include radio waves,
microwaves, visible light
 Sound energy - vibrations

Work
W=F x
 W = work in joules
 F = force in newtons

x = change in displacement (same
direction) in meters

Law of Conservation of Energy
 Energy
may not be created or
destroyed.
 All forms of energy can be
converted into other forms.
–Kinetic and potential energy
conversions are among the most
common.
Thermal energy and conservation
No system is perfect or efficient
 Some of the useful energy is
transformed to thermal energy
 Energy pyramid from life science
