Download Energy

Energy
DEFINITION
• the ability to cause a change
• common measurement unit = Joule (J)
FORMS
• energy exists in many different forms:
1.
2.
3.
4.
5.
6.
7.
8.
9.
potential
kinetic
mechanical
heat
chemical
nuclear
electrical
light
sound
(Gravitational) Potential Energy
• abbreviations: PE, GPE, and PEgravitational
• energy stored in a non-moving object due to
its position, shape, or composition in a
gravitational field
Kinetic Energy
• abbreviation: KE
• energy of motion
• all moving objects
have kinetic energy
Mechanical Energy
• total potential energy & kinetic energy of an
object
• ME = PE + KE
Heat
• Energy that moves from hot objects to cooler
ones
Chemical Energy
• energy stored in chemical bonds
Nuclear Energy
• Energy stored in the nucleus of an atom
Electrical Energy
• Energy of moving electrons
Light Energy
• Energy contained in electromagnetic waves
Sound Energy
• Energy produced by vibrating objects
Potential Energy Word Problems
A 4 kg rock is
sitting on a 3 m ledge.
How much gravitational
potential energy does it have?
GIVENS:
m = 4 kg h = 3 m g = 9.8m/s2
UNKNOWN:
PE
EQUATION:
PE = mgh
SUBSTITUTION: PE = (4 kg) x (9.8m/s2) x (3 m)
SOLUTION:
117.6 J
Kinetic Energy Word Problems
A 3 kg ball is rolling
at a velocity of 2 m/s.
How much kinetic energy does it
have?
GIVENS:
m = 3 kg v = 2 m/s
UNKNOWN:
KE
EQUATION:
KE = ½ mv2
SUBSTITUTION:
KE = ½ (3kg)(2m/s)2
SOLUTION:
6kgm/s2 = 6 J
LAW of CONSERVATION of ENERGY
Energy cannot be created or destroyed,
BUT
it can be transferred from one object
to another
AND
it can be changed, or converted, from one
form to another
Energy Transfer
• Occurs when one object passes some of its
energy to another object
• First object loses energy; second object
gains energy
• 3 main ways: conduction, convection, and
radiation
Conduction
• Energy is transferred within an
object or between objects that
are touching
• As particles in objects collide,
their energy is transferred
Convection
• Fluids (liquids & gases)
transport energy
from one place to
another
• Forms convection
currents
Radiation
• transfer of energy
through electromagnetic
waves
• radiation is felt as energy
is absorbed by a material
Energy Conversions
• AKA energy transformations
• Change of one form of energy into another
example
Electric Fan
• Electrical → kinetic
• When you plug in the fan,
electricity causes the
blades to move