Transcript Unit III Energy

Unit III Energy
Physical Science
Forms of Energy
Energy is the ability to
do work
• Measured in Joules (J) just like
work
• All matter has energy
General Forms of Energy
1. Kinetic Energy: KE = ½ m v2
The energy of motion. Anything that is
moving has kinetic energy.
Do these people have KE?
2. Potential Energy: PE = mgh
Energy that is stored or is not being used yet
Do these things have PE?
How to change KE
• Change the
mass or velocity
of an object
• If velocity is
doubled, KE is
quadrupled
Types of PE
Gravitational PE: depends on how
high off the ground an object is.
* the greater the height and mass
the object has the more
Gravitational PE it has
Elastic PE: the ability of an object to
rebound to its original shape or size
(we don’t have to calculate this one)
Types of Energy
1. Mechanical:
Energy of
everyday
objects
(anything with
mass and
volume)
2. Chemical
Energy: energy
that is stored in
chemical bonds
3. Electromagnetic Energy:
energy that is
related to charge
and magnetic
poles
4. Thermal Energy: energy that
is based on the internal motion
of particles in an object
(Heat and temperature)
5. Nuclear Energy: energy that
is contained in the nucleus.
Released when strong and
weak nuclear forces are
overcome
Energy Conversion
• When energy is transferred
between one type and another.
Example: burning gasoline
transfers chemical potential
into thermal energy
Energy Conversion
• In a perfect situation, the total
energy in a conversion is
conserved.
• Total Energy is all of the PE and
KE of a situation added
together.
• KE1 + PE1 = KE2 + PE2
KE and Friction
• Friction slows an object down
therefore it reduces the amount
of kinetic energy
• Increases the amount of
Thermal Energy
Practice
Problem
1. A 0.15 kg ball
is thrown into
the air and
rises to a
height of 20.0
m. How much
kinetic energy
did the ball
have initially?
2. A 1.25 kg steel ball with
a kinetic energy of 0.25 J
rolls along a horizontal
track. How high up an
inclined track will the ball
roll if friction can be
ignored?
Renewable vs. Non Renewable
• Renewable: forms
of energy that can
reproduce fast
enough with use
• Nonrenewable:
energy that
cannot reproduce
itself