Chapter 13 Energy & Power
How is energy
important to us?
Energy



The ability to do work or
cause change is called
energy.
Works is the transfer of
energy.
Two types of energy:
–
–
Kinetic energy is energy
of motion.
Potential energy is energy
of position or shape.
Kinetic Energy



Kinetic energy = mass x
(velocity)2/2
Doubling the mass, doubles
the kinetic energy.
Double the velocity, quadruple
the kinetic energy.
Potential Energy

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Elastic potential energy is
energy stored when an object
is stretched or compressed.
Gravitational potential energy
is energy stored because of
the height of the object’s
position.
Gravitational potential energy
= weight x height.
Energy is measured in units
called Joules.
Forms of Energy



Mechanical energy is the
energy associated with the
motion or position of an
object.
Thermal energy is the total
energy of the particles in an
object.
Chemical energy is the
potential energy stored in
chemical bonds that hold
chemical compounds
together.
Forms of Energy



Electrical energy is moving
electric charges produce
electricity and energy.
Electromagnetic energy
travels in waves and have
both electrical & magnetic
properties.
Nuclear energy is energy
stored in the nucleus of an
atom and is released during
nuclear reactions.
In which units do we measure energy?
1
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3.
20
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2.
gram
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kilogram
Newton
gr
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1.
When you wind up a rubber band on an
airplane, what type of energy does this
represent?
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4.
4
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3.
16
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2.
Chemical potential
energy
Elastic potential
energy
Gravitational
potential energy
Kinetic energy
C
1.
Which type of energy travels in waves?
1.
2.
3.
4.
Electrical
Electromagnetic
Mechanical
Nuclear
18
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Energy Conversion and Conservation


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A change from one form of
energy to another is called
energy conversion.
Most forms of energy can be
converted into any other
form.
What is the energy
conversion of the flashlight
in the diagram on the right?
Energy Conversion

What is the energy
conversion for the fan
in the diagram on the
right?
Conservation of Energy


Law of conservation of
energy states that when
one form of energy is
converted to another,
no energy is destroyed
in the process.
According to the law of
conservation of energy,
energy cannot be
created or destroyed.
Fossil Fuels




Fossil fuels are formed
from the burying of plants
and animals.
Include coal, petroleum and
natural gas.
Fossil fuels contain energy
that came from the sun.
Fossil fuels can be burned
to release the potential
chemical energy stored
millions of years ago.
Power


Power is the rate at which
work is done or the amount
of work done in a unit of
time.
Power is calculated by
dividing the amount of work
done by the amount of time
taken to do work.
– Power = work/time
– Power = force x
distance/time
– Power is measured in
watts.
Power (continue)


Power is the rate at which
energy is transferred form
one object to another or
converted from one form to
another.
One horsepower is equal to
746 watts.
Pendulum Lab

Purpose: The purpose of
this lab is for the students to
learn which factor affects the
period of the swing of a
pendulum.

Materials:
–
–
–
–
–
3 different weights
meter stick
string
stopwatch
ring stand
Pendulum Lab

1.
2.
3.
4.
Procedure:
Tie a weight to the end of a string.
Attached the other end of the string to the ring
stand.
Pull the weight back a standard distance and
release the weight.
Time how long it takes for ten cycles of the
pendulum. Enter this data on the data table.
Pendulum Lab
5.
6.
7.
8.
Divide the time by ten to find the time for a single
swing.
Change the weight and repeat procedures 1-5.
Change the weight and repeat procedures 1-5.
Next change the length of the string and keep the
weight the same. Repeat procedures 1-5.
Pendulum Lab
9.
10.
11.
Change the length of the string a second time and
keep the weight the same. Repeat procedures 1-5.
Change the angle of release. Repeat procedures
1-5.
Change the angle of release. Repeat procedures
1-5.
Pendulum Lab

1.
2.
3.
4.
Questions:
Make a drawing of the pendulum. Indicate on the
diagram the positions of the maximum potential
energy and the maximum kinetic energy.
What were the variables in this experiment? Which
was the manipulative variable and which was the
responding variable?
Explain how the Law of the Conservation of Energy
is observed in this experiment.
What forces act on the pendulum to stop its motion?
Pendulum Lab

Look at the diagram on the
right.
Formative Assessment Review

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What are the two types of energy?
(kinetic and potential)
Which type of energy is energy of motion?
(kinetic)
Which type of energy is stored energy?
(potential)
Which type of energy is stored in a stretched rubberband or
compressed spring?
(elastic potential energy)
Which type of energy is stored because of the position of the
object?
(gravitational potential energy)
Formative Assessment Review
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What is the formula for calculating kinetic energy?
(KE=mv2/2)
What is the formula for calculating gravitational potential
energy?
(GPE=w x h or GPE=m x g x h)
Name six forms of energy.
(mechanical, thermal, chemical, electrical, electromagnetic,
nuclear)
Which law states that energy is neither created or destroyed?
(Law of Conservation of Energy)
What is the formula for calculating Power?
(P=w/t)
Formative Assessment Review
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What unit is power measured?
(watt)
What unit is work or energy measured?
(joule)
What do we call the ability to do work or cause change?
(energy)
What happens to kinetic energy if the mass is doubled?
(doubles)
What happens to kinetic energy if the velocity doubles?
(quadruples)
_______________ is the transfer of energy.
(work)
Formative Assessment Review
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What is the numerical value of gravitational acceleration?
(9.8 m/s2)
What energy is associated with motion or position?
(mechanical)
What energy is associated with the total energy of the particles
of an object?
(thermal)
What energy is associated with the potential energy stored in
chemical bonds?
(chemical)
What energy is produced by moving electric charges?
(electrical)
Formative Assessment Review
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What energy travels in waves?
(electromagnetic)
What energy is stored in the nucleus of an atom?
(nuclear)
What is it called when an energy form changes to another form
of energy?
(converstions)
Who stated that energy can be created by destroying matter?
(Einstein)
How is energy released from fossil fuel?
(burning)
Formative Assessment Review
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What energy is mechanical energy converted to by friction?
(thermal)
Name three fossil fuels.
(coal, petroleum, natural gas)
_______________ is the rate at which work is done.
(power)
How many watts are in one horsepower?
(746)