Download energy - Science 6

ENERGY – is the ability to do work or cause change
Work is a transfer of energy.
When energy is transferred, the object upon which work is done
gains energy.
POWER = energy transferred (work)
time
KINETIC ENERGY
- is energy an object has due to motion.
-it depends on MASS and VELOCITY
- kinetic energy INCREASES when either mass or velocity
INCREASES
KINETIC ENERGY= ½ ½ 1/2 x mass x velocity2
*changing the velocity has a greater effect than changing the
mass*
COMPARE the following:
1) a 20kg object moving at 10 km/hr:
KE = 1/2(20)(102) = (10)(100) = 1,000
2) a 40 kg object moving at 10 km/hr
KE = 1/2(40)(102) = (20)(100) = 2,000
3) a 20 kg object moving at 20 km/hr
KE = 1/2(20)(202) = (10)(400) = 4,000
POTENTIAL ENERGY
- is stored energy as a result of position or shape.
-gravitational PE is related to the object’s
HEIGHT and WEIGHT
- gravitational potential energy INCREASES when either weight or
height INCREASES
Gravitational Potential energy = weight x height
Example: height or the weight of a skier on a jump
will effect the GPE
ELASTIC POTENTIAL ENERGY
- is potential energy associated with objects that can be stretched
or compressed
Examples: rubber band, bow and arrow, sponge
Potential and Kinetic energy work in opposing
pairs!
As one increases, the other decreases!
Forms of Energy
1) Mechanical Energy – this is energy associated with position and motion
of an object.
An object with mechanical energy can do work on another object!
ME = WORK
ME = potential energy + kinetic energy
2) Thermal energy – is the total potential and kinetic energy of the particles
in an object
For example: hot lava has high thermal energy
KE = thermal energy
3) Electrical Energy – is the energy of electric charges (getting a shock)
For example: lightening, battery energy, outlets
4) Chemical Energy – is the potential energy stored in chemical bonds that
hold compounds together. Stored in food, cells etc.)
For Example: when your body breaks food down, it breaks the
bonds holding the atoms together, this RELEASES ENERGY that our bodies can
now use.
5) Nuclear Energy – is the energy stored in the nucleus of an atom. It is released
during a nuclear reaction:
fission – the nucleus splits and releases energy
fusion – nuclei fuse (join) together and release
energy. This occurs on the SUN.
6) Electromagnetic Energy – is energy that travels in waves. These have
electrical and magnetic properties.
For Example: sunlight, radio waves, UV rays, X-rays
ENERGY TRANSFORMATIONS & CONSERVATION
Most forms of energy can be transformed into other forms.
An ENERGY TRANSFORMATION
-is a change from one form of energy to another.
Single transformation:
one form
another form
Examples:
1) A toaster turns electrical energy to thermal energy
2) Cell phone turns electrical to electromagnetic
3) Your body turns chemical energy to mechanical energy
Multiple transformations:
one form another form
another form
For Example:
1) A match turns mechanical to thermal to chemical back to thermal to electromagnetic!
2) A car turns electrical (spark) to thermal to chemical to thermal to mechanical and back to
electrical!
Transformations between KINETIC & POTENTIAL
This is the most common energy transformation!
Energy transformation in a pole vault:
kinetic elastic potential graviational potential kinetic
(falling)
CONSERVATION of ENERGY says:
“Energy CANNOT be created OR destroyed!
It can only be converted into other forms.”
The TOTAL amount of energy is the SAME BEFORE AND AFTER any
transformation!!
1) Friction causes some kinetic energy to become thermal
energy (heat).
Think about rubbing your hands together!
2) Some matter can be transformed into energy, so in reality:
“Matter and energy together are always
conserved!”