Slide 2 START Slide 3 Lesson Objectives Concepts of energy and
forms of energy will be discussed in this lesson. These concepts
are combined with the work-energy theorem to provide a convenient
means of analyzing an object or system of objects moving between an
initial and final state. In the end of the lesson, students will be
able to discuss and recognize energy. TOC Slide 4 Prerequisites
This Lesson does not require specific science's knowledge
background. However basic understanding in several science's
concepts like momentum, velocity, force, and velocity are strongly
recommended. TOC Slide 5 Table of Content Home Home Lesson
Objectives Lesson Objectives Prerequisite Prerequisite Concepts of
Energy Energy Energy Works Works Summary & Practice Summary
& Practice Forms of Energy Potential Definition Definition
Gravitational Potential Energy Gravitational Potential Energy
Elastic Potential Energy Elastic Potential Energy Summary &
Practice Summary & Practice Kinetic Definition Definition
Summary & Practice Summary & Practice Mechanical Definition
Definition Summary & Practice Summary & Practice Evaluation
Evaluation TOC Slide 6 Concepts of Energy What? Energy is ability
to do work. Work is displacement of an object caused by force acts
upon the object. Why? When you work on an object, you transfer
energy (Force) to that object Whenever work is done, energy is
transferred or transformed to another systems Illustration AB TOC
Energy Slide 7 Concepts of Energy cont.. Works Work can be
expressed by the following equation. where F is the force, d is the
displacement and the angle (theta ) is the angle between the force
and the displacement vector. Perhaps the most difficult aspect of
the above equation is the angle "theta. Please see the illustration
beside. Displacement can be a distance but sometimes, it is not, to
make it easy displacement is a horizontal distance between start
and end position. the standard metric unit of works is the Joule
(J). One Joule is equivalent to one Newton of force causing a
displacement of one meter. In other words: 1 Joule = 1 Newton x 1
Meter = 1 kg x m 2 /s 2 W = F x d x Cos CLICK TO PLAY F d TOC F d
=0 o F d =180 o F d =90 o Slide 8 Concepts of Energy cont.. Summary
Three key ingredients to work - force, displacement, and cause In
works mathematic equation, the angle (theta ) is the angle between
the force and the displacement vector. And displacement (d) is a
horizontal distance between start and end position. Practice A 10-N
frictional force slows a moving block to a stop after a
displacement of 5.0 m to the right. done ? Only F frict does work.
F grav and F norm do not do work since a vertical force cannot
cause a horizontal displacement. W frict =(10 N) * (5 m) * cos (180
degrees) = -50 Joules TOC Slide 9 Forms of Energy The two examples
above illustrate the two forms of potential energy to be discussed
in this lesson - gravitational potential energy and elastic
potential energy. gravitational potential energelastic potential
energy. Potential Energy An object can store energy as the result
of its position. For example, the heavy ball of a demolition
machine is storing energy when it is held at an elevated position.
This stored energy of position is referred to as potential energy.
Similarly, a drawn bow is able to store energy as the result of its
position. When assuming its usual position (i.e., when not drawn),
there is no energy stored in the bow. Yet when its position is
altered from its usual equilibrium position, the bow is able to
store energy by virtue of its position. This stored energy of
position is referred to as potential energy. Potential energy is
the stored energy of position possessed by an object. TOC Slide 10
Potential Energy cont.. PE grav = m * g * h In the above equation,
m represents the mass of the object, h represents the height of the
object and g represents the acceleration of gravity (g=9.8 m/s/s on
Earth). Gravitational Potential Energy Gravitational potential
energy is the energy stored in an object as the result of its
vertical position or height. The energy is stored as the result of
the gravitational attraction of the Earth for the object. The
gravitational potential energy of the massive ball of a demolition
machine is dependent on two variables - the mass of the ball and
the height to which it is raised. There is a direct relation
between gravitational potential energy and the mass of an object.
More massive objects have greater gravitational potential energy.
There is also a direct relation between gravitational potential
energy and the height of an object. The higher that an object is
elevated, the greater the gravitational potential energy. These
relationships are expressed by the following equation: TOC CLICK TO
PLAY h m g Slide 11 Potential Energy cont.. If a spring is not
stretched or compressed, then there is no elastic potential energy
stored in it. The spring is said to be at its equilibrium position.
The equilibrium position is the position that the spring naturally
assumes when there is no force applied to it. In terms of potential
energy, the equilibrium position could be called the zero-potential
energy position. There is a special equation for springs which
relates the amount of elastic potential energy to the amount of
stretch (or compression) and the spring constant. Elastic Potential
Energy Elastic potential energy is the energy stored in elastic
materials as the result of stretching or compressing. Elastic
potential energy can be stored in rubber bands, trampolines,
springs, an arrow drawn into a bow, etc. The amount of elastic
potential energy stored in such a device is related to the amount
of stretch of the device - the more stretch, the more stored
energy. Springs are a special instance of a device which can store
elastic potential energy due to either compression or stretching. A
force is required to compress a spring; the more compression there
is, the more force which is required to compress it further. For
certain springs, the amount of force is directly proportional to
the amount of stretch or compression (x); the constant of
proportionality is known as the spring constant (k). TOC CLICK TO
PLAY x x k Slide 12 1.A teacher applies a force to a wall and
becomes exhausted. This statement is a example of work (Y N). 2.A
book falls off a table and free falls to the ground. This statement
is a example of work (Y N). 3.A cart is loaded with a brick and
pulled at constant speed along an inclined plane to the height of a
seat- top. If the mass of the loaded cart is 3.0 kg and the height
of the seat top is 0.45 meters, then what is the potential energy
of the loaded cart at the height of the seat-top? Potential Energy
cont.. SUMMARY To summarize, potential energy is the energy which
is stored in an object due to its position relative to some zero
position. An object possesses gravitational potential energy if it
is positioned at a height above (or below) the zero height. An
object possesses elastic potential energy if it is at a position on
an elastic medium other than the equilibrium position. PRACTICE N.
This is not an example of work. The wall is not displaced. A force
must cause a displacement in order for work to be done. Y. This is
an example of work. There is a force (gravity) which acts on the
book which causes it to be displaced in a downward direction (i.e.,
"fall"). PE = m*g*h PE = (3 kg ) * (9.8 m/s/s) * (0.45 m) PE = 13.2
J TOC Slide 13 Forms of Energy KINETIC ENERGY Kinetic energy is the
energy of motion. An object which has motion - whether it be
vertical or horizontal motion - has kinetic energy. There are many
forms of kinetic energy - vibrational (the energy due to
vibrational motion), rotational (the energy due to rotational
motion), and translational (the energy due to motion from one
location to another). To keep matters simple, we will focus upon
translational kinetic energy. The amount of translational kinetic
energy (from here on, the phrase kinetic energy will refer to
translational kinetic energy) which an object has depends upon two
variables: the mass (m) of the object and the speed (v) of the
object. The following equation is used to represent the kinetic
energy (KE) of an object. TOC time :5 43210 CLICK TO PLAY 10 864 2
0 distance: V = Speed of object = distance/time = d/t (m/s) KE = *
m * v 2 = * m * d 2 /t 2 V= 2 m/s s m d=10m Slide 14 Kinetic Energy
cont.. Summary Kinetic energy is a scalar quantity; it does not
have a direction. The standard metric unit of measurement for
kinetic energy is the Joule Kinetic energy of an object is directly
proportional to the square of its speed. For example; for a twofold
increase in speed, the kinetic energy will increase by a factor of
four. Practice Determine the kinetic energy of a 625-kg roller
coaster car that is moving with a speed of 18.3 m/s! If the roller
coaster car in the above problem were moving with twice the speed,
then what would be its new kinetic energy? KE = 0.5*m*v 2 KE =
(0.5) * (625 kg) * (18.3 m/s) 2 KE = 1.05 x10 5 Joules If the speed
is doubled, then the KE is quadrupled. Thus, KE = 4 * (1.04653 x 10
5 J) = 4.19 x 10 5 Joules. or KE = 0.5*m*v 2 KE = 0.5*625 kg*(36.6
m/s) 2 KE = 4.19 x 10 5 Joules TOC Slide 15 Forms of Energy As
discussed earlier, there are two forms of potential energy
discussed in our course - gravitational potential energy and
elastic potential energy. Given this fact, the previous equation
can be rewritten: potential energy TME=(PEgav+PEspring)+KE
Mechanical Energy The energy acquired by the objects upon which
work is done is known as mechanical energy. Mechanical energy is
the energy which is possessed by an object due to its motion or due
to its position. Mechanical energy can be either kinetic energy
(energy of motion) or potential energy (stored energy of position)
or combination of these. The total amount of mechanical energy is
merely the sum of the potential energy and the kinetic energy. This
sum is simply referred to as the total mechanical energy :kinetic
energy potential energy TME= PE + KE CLICK TO PLAY TME= PE TME= PE
+ KETME= KE TOC Slide 16 Mechanical Energy cont.. Summary Three key
ingredients to work - force, displacement, and cause In works
mathematic equation, the angle (theta ) is the angle between the
force and the displacement vector. And displacement (d) is a
horizontal distance between start and end position. Practice A 10-N
frictional force slows a moving block to a stop after a
displacement of 5.0 m to the right. done ? Only F frict does work.
F grav and F norm do not do work since a vertical force cannot
cause a horizontal displacement. W frict =(10 N) * (5 m) * cos (180
degrees) = -50 Joules TOC Slide 17 EVALUATION Now, You have learned
basics concepts about energy. Energy forms are either potential or
kinetic. Potential energy comes in forms that are stored.
Mechanical energy. Mechanical energy can be either kinetic energy
(energy of motion) or potential energy (stored energy of position)
or combination of these.kinetic energypotential energy To check
your understanding about previous lesson. Lets begin the test !
Remember this test is scored. START Summary Slide 18 Evaluation
1.Please define three key elements of work: CHECK SCORE GO TO THE
NEXT QUESTION Slide 19 Evaluation cont 2.A waiter carries a tray
full of meals above his head by one arm straight across the room at
constant speed. This statement is a example of work. YES NO SCORE
Slide 20 Feedback INCORRECT! Remember !!! There are three key
ingredients to work - force, displacement, and cause Click to try
again SCORE Slide 21 Feedback CORRECT! This is not an example of
work. There is a force (the waiter pushes up on the tray) and there
is a displacement (the tray is moved horizontally across the room).
Yet the force does not cause the displacement. To cause a
displacement, there must be a component of force in the direction
of the displacement. GO TO THE NEXT QUESTION SCORE Slide 22
Evaluation cont 3.A rocket accelerates through space. This
statement is a example of work. YES NO SCORE Slide 23 Feedback
INCORRECT! Remember !!! There are three key ingredients to work -
force, displacement, and cause Click to try again SCORE Slide 24
Feedback CORRECT! This is an example of work. There is a force (the
expelled gases push on the rocket) which causes the rocket to be
displaced through space. SCORE GO TO THE NEXT QUESTION Slide 25
Evaluation cont 4.Missy Diwater, the former platform diver for the
Ringling Brother's Circus, had a kinetic energy of 12 000 J just
prior to hitting the bucket of water. If Missy's mass is 40 kg,
then what is her speed? m/s CHECK SCORE GO TO THE NEXT QUESTION
Slide 26 Evaluation cont 5.A 900-kg compact car moving at 60 mi/hr
has approximately 320 000 Joules of kinetic energy. Estimate its
new kinetic energy if it is moving at 30 mi/hr. (HINT: use the
kinetic energy equation as a "guide to thinking.") SCORE CHECK
FINISH Slide 27 Please Wait SHOW FINAL RESULT Slide 28 TOC YOU HAVE
CORECT ANSWERS FROM TOTAL 5 QUESTION ITEM You Need To Retake This
Lesson Again OH NO....
