8

SCIENCE 8
Quarter I-Module 3
Work, Power, and Energy
S8FE-IA-16

SA RTY
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FO T PR
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Science – Grade 8
Alternative Delivery Mode
Quarter 1– Module 3: Work, Energy and Power
First Edition, 2020

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over them.

Published by the Department of Education - Region III

Secretary : Leonor M. Briones
Undersecretary : Diosdado M. San Antonio

Development Team of the Module

Author: Anna Gladys C. Mendoza

Language Reviewer: Monica P. Sotto
Content Editor: Jan Michael C. Sotto
Illustrator: Hazel C. Santos
Layout Artist: Francisco C. Adriano

Management Team
Gregorio C. Quinto, Jr., EdD
Chief, Curriculum Implementation Division
Rainelda M. Blanco, PhD
Education Program Supervisor - LRMDS
Agnes R. Bernardo, PhD
EPS-Division ADM Coordinator
Marinella P. Garcia Sy, PhD
EPS – Science
Glenda S. Constantino
Project Development Officer II
Joannarie C. Garcia
Librarian II

Department of Education, Schools Division of Bulacan

Curriculum Implementation Division
Learning Resource Management and Development System (LRMDS)
Capitol Compound, Guinhawa St., City of Malolos, Bulacan
Email address: lrmdsbulacan@deped.gov.ph
 8
Science
Quarter I - Module 3
Work, Energy, and Power
S8-FE-IA-16
 Introductory Message

For the Facilitator:

Welcome to the Science 8 Alternative Delivery Mode (ADM) on Work, Energy and Power.

This module was collaboratively designed, developed and reviewed by educators from
public institutions to assist you, the teacher or facilitator, in helping the learners meet the
standards set by the K to 12 Curriculum while overcoming their personal, social, and
economic constraints in schooling.

This learning resource hopes to engage the learners into guided and independent learning
activities at their own pace and time. Furthermore, this also aims to help learners acquire
the needed 21st century skills while taking into consideration their needs and
circumstances.

In addition to the material in the main text, you will also see this box in the body of the
module:

Notes to the Teacher

This contains helpful tips or strategies that will
help you in guiding the learners.

As a facilitator, you are expected to orient the learners on how to use this module. You also
need to keep track of the learners’ progress while allowing them to manage their own
learning. Furthermore, you are expected to encourage and assist the learners as they do
the tasks included in the module.

For the Learner:

Welcome to the Science 8 Alternative Delivery Mode (ADM) Module on Work, Energy and
Power!
This module was designed to provide you with fun and meaningful opportunities for guided
and independent learning at your own pace and time. You will be enabled to process the
contents of the learning resource while being an active learner.
This module has the following parts and corresponding icons:

This will give you an idea of the skills or

What I Need to Know competencies you are expected to learn in the
module.

This part includes an activity that aims to check

what you already know about the lesson to take. If
What I Know
you get all the answers correct (100%), you may
decide to skip this module.

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 This is a brief drill or review to help you link the
What’s In
current lesson with the previous one.

In this portion, the new lesson will be introduced to

What’s New you in various ways; a story, a song, a poem, a
problem opener, an activity or a situation.
This section provides a brief discussion of the
What is It lesson. This aims to help you discover and
understand new concepts and skills.
This comprises activities for independent practice to
solidify your understanding and skills of the topic.
What’s More
You may check the answers to the exercises using
the Answer Key at the end of the module.
This includes questions or blank sentence/
What I Have Learned paragraph to be filled in to process what you learned
from the lesson.
This section provides an activity which will help you
What I Can Do transfer your new knowledge or skill into real life
situations or concerns.

This is a task which aims to evaluate your level of

Assessment
mastery in achieving the learning competency.

In this portion, another activity will be given to you to

Additional Activities
enrich your knowledge or skill of the lesson learned.

Answer Key This contains answers to all activities in the module.

At the end of this module you will also find:

References - This is a list of all sources used in developing this module.
The following are some reminders in using this module:
1. Use the module with care. Do not put unnecessary mark/s on any part of the
module. Use a separate sheet of paper in answering the exercises.
2. Don’t forget to answer What I Know before moving on to the other activities
included in the module.
3. Read the instruction carefully before doing each task.
4. Observe honesty and integrity in doing the tasks and checking your answers.
5. Finish the task at hand before proceeding to the next.
6. Return this module to your teacher/facilitator once you are through with it.
If you encounter any difficulty in answering the tasks in this module, do not hesitate to
consult your teacher or facilitator. Always bear in mind that you are not alone.
We hope that through this material, you will experience meaningful learning and gain
deep understanding of the relevant competencies. You can do it!

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 What I Need to Know

This module will help you to identify and explain the factors that affect
potential and kinetic energy. It will also help you to understand the connection of
energy to work and power. Several activities are provided for you to perform
strengthening your knowledge and skills regarding the topics.
Have fun and enjoy learning the lesson of work, energy and power.
At the end of this module, you are expected to:
1. calculate for the work done if the force applied is parallel to the displacement of an
object;
2. differentiate potential energy from kinetic energy and explain the relationship of
mass, speed, and position to the energy possessed by an object;
3. calculate power used by a force acting on a moving body; and
4. appreciate the importance of the work, energy and power to real-life activities.

What I Know

Write the letter of your answer in a separate sheet of paper. Use capital letters only.
1. How much work is done by Popoy when he pushed their dining table with a constant
force of 110 N across a distance of 3 meters?
A. 300 J B. 310 J C. 320 J D. 330 J

2. For work to happen all conditions must be met except:

A. The object must have a certain displacement.
B. The direction of the force must be perpendicular to the motion.
C. A force must be acting on the object.
D The direction of the force must be the same as the direction of the motion.
3. Pepay did 200 J of work in lifting the potted plant from the floor up to the wooden
platform. If the height of the platform is 1.5 m, how much energy did she use to do this?
A. 150 J B. 200 J C. 250 J D. 300 J
4. Which of the following factors does not affect the gravitational potential energy of an
object?
A. acceleration due to gravity C. mass
B. height D. speed
5. What is the maya’s kinetic energy if it flies at a constant speed of 7.5 with a mass of
0.15 kg?
A. 4.20 J B. 4.21 J C. 4.22 J D. 4.23 J

6. How much potential energy is in a 23 kg box that has to be lifted to a height of 3 m?

A. 600 J B. 656.2 J C. 676.2 J D. 696.2 J

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7. Which of the following is true when a force applied has a certain angle to the motion of
the object?
A. The resulting work will be greater than when the direction of force and motion is
the same.
B. The resulting work will be lesser than when the direction of force and motion is
the same.
C. The work done will be the same as the direction of force and motion is the same.
D. There will be no work done.
8. In the given situations, which shows work done scientifically?
A. Pepay lifting a basket of vegetables.
B. Popoy carrying a large squash on his shoulder.
C. Popoy pushing the large trunk of a Narra tree.
D. Pepay holding a bilao of suman in the air.
9. The two cars with the same mass but has different speed are moving along Mc Arthur
highway. Which of the cars has more kinetic energy?
A. the car with a greater speed C. both cars
B. the car with a lesser speed D. neither of the cars
10. Which of the following situations has kinetic energy?
A. A stone that sits at the top of a hill C. A piece of the burger before it is eaten
B. A painting that hangs on the wall D. A ball that rolls across the road
11. If the mango and coconut will fall from the same height, which of the two will have
greater potential energy?
A. coconut C. both coconut and mango
B. mango D. none of the fruits
12. Pepay did 200 J of work in lifting the potted plant from the floor up to the wooden
platform. If she had this in 4 s, how much power did she use?
A. 50 J B. 50 KW C. 50 N D. 50 W
13. Which of the following best describes power?
A. the capacity to do work
B. the product of the force and the displacement
C. the push or pull exerted on an object
D. the rate of doing work or using energy

14. Tatay Pedro’s diesel-powered tiller has a power rating of 9,000 W. How much work
it can do in 5 s?
A. 40 000 J B. 45 000 J C. 50 000 J D. 55 000 J
15. The two boys of the same weight climbed the same stairs and arrived at the top at
different times. Which of the following conclusions best fit the situation?

A. They both did the same amount of work and used the same power.
B. They did a different amount of work but used the same power.
C. They did the same amount of work but used different power.
D. They both did a different amount of work and had no power.

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 What’s In

Read the story of Pepay and Popoy.

Every day is a blessed day to Sitio Pagkakaisa after the Covid-19 pandemic
broke out. Many of the residents cannot go back into their normal lives because of the
threat brought by the situation. Despite this, they still stand strong in their sitio. It is
because of the hope that through their bayanihan, they will be able to adapt to what they
call the "new normal". This hope sparks the desire of the Santos siblings, Pepay and
Popoy, to continue their education even though they cannot go to school just like before.
They try to look at every situation they have as a chance to learn.
One day in the Santos residence, the
youngest of the family, Popoy, is sweeping their
backyard. Suddenly, Pepay, his “Ate”, shouted
his name. She came rushing towards him
waving something white in her hand. Upon a
closer look, he identified that it is a facemask
made by his mother. He forgot to wear it before
he went to their backyard to sweep. This earned
him a good scolding from her Ate.
While listening to her Ate Pepay, a wishful thought came into his mind and shared
it with her. He said that if only he has a superpower, then, he will work hard to help the
patients and the frontliners to end the pandemic. Pepay showed a small smile in her face
while realizing that her brother is full of wonders. She gathered all her energy to explain
that even without a superpower but they work together, the pandemic will end.
After Pepay talked to her brother, she then helped him in sweeping the backyard.
They finished the work quickly and went to see their mother, Nanay Perla, in the kitchen.
They were asked by Nanay Perla to harvest vegetables and fruits in the vacant lot near
their house. During the quarantine period, Nanay Perla and Tatay Pedro planted several
seedlings in the lot so they can have a source of food when they cannot go to the
market. Both Pepay and Popoy were excited to harvest the labor of their parents. They
immediately pulled the cart out of the garage and pushed it fast towards the vacant lot.

Do you remember the highlighted words in the story? Can you guess what the
words referred to in Science? You got it right if you think it is Force. In the earlier module,
force is described as the push or pull applied to an object. When the force is applied to
an object, it produces changes in the motion. It makes the object move, stop, and change
speed or direction. Therefore, force affects motion. Aside from it, the mass and acceleration
also affect the motion of the object. This was all explained by the great genius Isaac
Newton in his Laws of Motion.

Let us now look at Figure 1 below that shows Pepay and Popoy harvesting
vegetables and fruits in the lot. Observe it before you proceed.

What’s that LAW?

Identify the Laws of Motion being described in the statement. Write Inertia if the
statement pertains to the first law, Acceleration for second law, and Interaction for the
third law. Do this in a separate sheet of paper.

9
______1. A rolling tomato on the ground that is about
to crash onto a big stone
______2. Popoy being able to walk towards the cart
______3. Pepay pushing a heavy cart slower than
before
______4. A bird flying around the lot
______5. A handful of leaves that stays still at the
corner Figure 1
Force plays a big role in Newton’s Law of Motion. It is also important for work to
happen. How? Let us find out.

Notes to the Teacher

The activities in this module are arranged with increasing difficulty so learners can
gradually master the desired learning competency. Offer assistance whenever
necessary for the learners to complete each task. Make use of the provided activities
for the learning process to be successful.

What’s New

Based on the story of Pepay and Popoy, who do you think did most of the work?
A. WORK on it!
Analyze the figures and answer the questions in a piece of paper.

A B A B
Covered a distance of 5 m Covered a distance of 10 m
Figure 2: Popoy pushing the cart Figure 3: Pepay pushing a cart
Questions:
1. Who do you think did most of the work? ____________________________________
2. Why do you think so? __________________________________________________
Let us now have a simple hands-on activity about work.
B. Work on this!
Follow the instructions carefully and complete the table in a separate sheet of
paper.
1. Get a book.
2. Lay the book on top of any flat surface.
3. Lift the book about 1-foot-high then put it down.
4. Push the book away from you.
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 If yes
Did you apply
Action taken Direction of the Direction of the
force?
Force movement
Lifting the book
Pushing the book
What you did in the activity work on this are examples of work. You might think that
you exerted little effort in doing it so. How can be it called work? Remember that in
Science, there is a specific meaning for work. Let us now find out!

Lesson 1: Making it WORK!

What is It

In the simple activity, the word WORK, when used in our daily lives, can refer to a
job, a task to be accomplished, or an activity that needs effort and time. But in Science,
especially Physics, work means a force applied to an object that resulted in a
movement.
When you lifted the book, you applied a force with a magnitude equivalent to its
weight. This caused the book to move upward and the distance moved by the book as a
result of the applied force is called displacement. Hence, scientific work was done.
It was also the same when you pushed the book away from yourself. The book
moved in the same direction as you applied the force. Therefore, if you exerted a force on
the book and it does not move, then there will be no work done.
You might have observed that in both situations the force and displacement have
the same direction or parallel to each other. What if the force and displacement are not in
the same direction, like if they are perpendicular to each other, will there be work done? In
this case, no work will be done in the situation.

Putting it Together!
From the discussion, let us try to describe what is work by completing the
paragraph below. Write your answer in a separate sheet of paper.
In order for work to happen, there must be a/an _________(energy, force) and a
displacement. However, there will be no work done if the force applied does not cause
any ____________(distance, movement) . Work is considered done if the __________
(distance, magnitude) of the force is __________(different, same) with the displacement.
Hence, there is no work when a force is applied __________(parallel, perpendicular) to

Now that you have understood what work means in Science, let us define it
further. Work can also be described as the product of the magnitude of the force and the
displacement covered by an object.
Mathematically, work can be expressed using this equation.
Where:
W = Fd W – the magnitude of work done
F – Force applied parallel to the displacement
d - displacement

11
 What is the SI unit used to describe work? You may have recalled that the unit of
force in the previous lesson is or Newton (N) and the unit of displacement is meter
(m).
Hence, The unit of Joule (J) was named after the
Unit of work = (N)(m) English physicist, James Prescott Joule. One
Unit of work = N·m or J Joule or Newton-meter of work means a force of
one Newton is exerted on an object that covered
a distance of one meter.

TRICK STOP!
Before you proceed in calculating, remember that it is important to use the
appropriate formula for a problem. Note that not all problems have the same set-up.
So here is a simple trick in manipulating the formula of work.
The circle on the left will be your pie of formula. Let’s say
you have identified in the problem that the missing factor is
Force. To determine the right formula, place your thumb on
W the part of the pie where F is located. The factors left in the
pie will be as given. So your formula to use will be F = . This
F d means that the quotient of Work and displacement will be the
magnitude of the force.
Try it with work and distance and see the result.

Let us say that for the cart to move, Pepay and Popoy must exert a force of 150 N.
Analyze Figure 2 to determine the amount of work done by Popoy.

Step 1: Identify the given and what is missing in the

problem. F = 150 N d=5m W=?
F =150N
Step 2: Use the pie formula trick to determine the
appropriate formula. W = Fd
Step 3: Substitute the identified given to the formula.
W = (150N)(5m)
Step 4: Apply the operation required in the formula to
A B
get the answer. Covered a distance of 5 m
W = 750 N·m or 750 J Figure 2: Popoy pushing the cart

For Popoy's work, there is a magnitude of 750 J. Now let us try to solve Pepay’s
work. Analyze the given and follow the steps we did earlier.
Step 1: Identify the given and what is missing in the
problem. F = 150 N d = 10 m W=?
Step 2: Use the pie formula trick to determine the
appropriate formula. W = Fd
Step 3: Substitute the identified given to the formula.
W = (150N)(10m)
Step 4: Apply the operation required in the formula to A B
get the answer. Covered a distance of 10 m
W = 1500 N·m or 1500 J Figure 3: Pepay pushing a cart
on a smooth road
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 For Pepay's work, there is a magnitude of 1500 J. Now from the computation we
did, who among Pepay and Popoy did most of the work? What do you think causes
Pepay's work to be higher than Popoy?

Think About It!

The direction of force and displacement will not always be in the same direction at
all times. Most of the time you do work in an angle, which means the direction of force
and displacement are not parallel nor perpendicular to each other.
The force exerted on a certain angle has two components with it. The force
parallel to the displacement and the force perpendicular to it. Which of the components
do you think is used for work? If you answer the component of the force that is parallel to
the displacement will be the one that is doing work, then you are correct.
The angle caused the resulting work much lesser compared to a work done when
the direction of the force and displacement is the same.

Lesson 2: Working with ENERGY!

In the previous lesson, you have learned how to analyze a situation that involves
work through understanding the direction of the force and the displacement. You have
also learned how to calculate the magnitude of the work done in a given situation. Let us
now see how work and energy are related to each other.
Imagine this, you threw a stone with all your might aiming at the guava tree along
the road. The stone hit a guava fruit which caused it to fall. Did you do work on the stone?
How about the stone? Did it do work on the fruit as well? If yes, where did it get its ability to
do work?
The stone will be able to do work because of energy and all things may possess it.
All objects capable of doing work has energy. This is because work is a way of transferring
energy. Hence, for work to happen, energy must be transferred or converted from one form
to another.
Let us perform a simple activity to test whether an object has an energy and can do
work.

EXPERIMENT 1: Energy that Rolls!

Objective: In this activity, you will be able to describe the relationship between
energy and work. Also, this will help you explain how the mass and height affect the
energy of an object.
Materials:
 3 pcs. of balls or any round object that is
capable of rolling (make sure that they have
different weights)
 A wooden plank or anything that can be
used as an inclined plane
 A ruler or any measuring instrument for
length
Figure 1: a ball placed at the highest  A small lightweight box
point of an inclined plank
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Procedure:
1. Gather all the materials in a wide area. Ask your parents or elder siblings for
assistance in doing this experiment.
2. Get the wooden plank and place the box at one end of it. The box’s purpose is to
catch the rolling ball.
3. Lift the other end of the plank with a height of 6 in. Use a ruler to measure it.
4. Arrange the balls from the lightest to the heaviest. Mark them as ball numbers 1 to 3.
5. Place ball number 1 at the highest point of the inclined plank. See Figure 1 for the
experiment set-up.
6. Gently push ball number 1 to roll on the plank and observe as it hits the box at the
bottom of the ramp.
7. Get the ruler and measure the distance of the box from its original place. Record this.
8. Do the same procedure from 5-7 for ball numbers 2 and 3.
9. Now, increase the inclination height of the plank by 12 in. Use your ruler for this.
10. Repeat the same procedure from 5-7 for ball numbers 1 to 3.
11. Fill out the table below and answer the guide questions in a separate sheet of paper.

Height of the in- Distance moved by the box (inch)

clined plank Ball number 1 Ball number 2 Ball number 3
At 6 inches
At 12 inches

Questions
1 Did you do work on the balls in this experiment? How about the balls to the box?
2 Is there an energy present when the ball rolls on the plank? How about when the ball
hits the box? Why do you say so?
3. If you did not place the ball on the plank and allow it to roll, will there be work done in
the situation, and will energy be present? Why?
4. Based on the experiment, which among the balls moved the box at a greater
distance when allowed to roll at the height of 6 in? Why do you think so?
5. Which among the balls possessed greater energy?
6. Is there a difference to the distance moved by the box when the height of the
inclination was increased to 12 in? What do you think caused this?
7. How do the weight and the height affect the energy of the ball?

You may be able to recall during your grade 7 Science some forms of energy such
as light, sound, electricity, and heat. You may also remember how these forms of energy
are being transferred. These can be through waves, moving particles, or electromagnetic
waves. And as mentioned earlier, energy can also be transferred through work. In your
experiment, you have witnessed how you have done work on the ball and how the ball did
work on the box. While this happens, energy is being transferred. For this to occur, two
forms of energy must be converted. These two are Kinetic Energy and Potential
Energy.
How can we define and differentiate these two forms of energy? Let us learn more
about kinetic and potential energy.

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Kinetic Energy
It is described as the energy possessed by an object in motion, just like a ball
rolling in an inclined plank, a stone hitting a guava fruit or a box moving away after being
hit by a ball. A moving object that changes its location from one point to another whether
in horizontal, vertical, or rotational has kinetic energy.
In the experiment, the movement of the box served
Trivia!
as an indication of how much energy was present in the
balls. When the plank was set at a height of 6 in, you might Kinētikos, a Greek word
have observed that the heaviest ball moved the box farther which means “of motion”
than the lightest ball. Also, you might have seen that the is where the name kinetic
faster the ball rolled, the greater it moved the box. This is was derived.
because kinetic energy is directly affected by two factors and
these are mass and speed.

MASS: SPEED
- The greater the mass of an object, the - The faster the object moves, the
greater the kinetic energy it may greater the kinetic energy it has.
possess. - When the speed is doubled and the
- When the mass is doubled, the kinetic mass doesn’t change, the kinetic
energy will be also doubled. energy will be quadrupled.

Mathematically, kinetic energy can be expressed using this equation:

Where:
KE – Kinetic Energy
KE = m – the mass of the object
v - the speed of the object

What is the SI unit used to describe energy? Right! It is Joule (J). On the other
hand, the mass uses kilogram (kg) and the speed uses meter per second ( ).

TRICK STOP!
 Always remember the value when converted to decimal is 0.5.
 When you see , it means that squared is only for the value of speed.
 Be aware of the given. If speed is present, then we are talking about kinetic energy.

Let us now try to understand the steps in calculating the kinetic energy of an object.
Let us say that in the experiment you did earlier, the moving ball number 1 has a speed of
2 and its mass is about 0.20 kg . What is the kinetic energy of the ball?

Step 1: Identify the given and what is missing

in the problem.

v=2 m = 0.20 kg KE = ?

Figure 2: a ball rolling on the plank

15
 Step 2: Substitute the identified given value to the formula.
This is the decimal value of
Formula: KE = KE = (0.5)(0.20 kg)(2 )2

Step 3: Square the value of speed and its unit.

KE = (0.5)(0.20 kg)(4 )
Step 4: Multiply the speed to the mass and then to 0.5 to get the value of KE.
KE = 0.4 kg or 0.4 J

What if we tried to increase the mass of the ball? Let us see its effect on kinetic
energy. Suppose that the third ball in your experiment has a mass of 0.80 kg and rolled at
the same speed of 2 . What is the kinetic energy of the ball?

Step 1: Identify the given and what is missing in the problem.

v=2 m = 0.80 kg KE = ?
Step 2: Substitute the identified given value to the formula.
Formula: KE = KE = (0.5)(0.80 kg)(2 )2
Step 3: Square the value of speed and its unit.
KE = (0.5)(0.80 kg)(4 )
Step 4: Multiply the speed to the mass and then to 0.5 to get the value of KE.
KE = 1.6 kg or 1.6 J

Now compare the kinetic energy of ball number 3 to ball number 1. What did you
observe? What if the mass of the ball remains 0.20kg but the speed of it becomes 4 .
What do you think will happen to its kinetic energy?

Potential Energy
An object at rest may also possess energy depending on its position or mass.
Potential energy is also known as stored energy. A ball at the highest point of an inclined
plank, a mango fruit about to fall from the ground and a stretched rubber of a slingshot
are all examples of objects that have potential energy. It is because these objects can do
work when the potential energy is converted into kinetic energy. Potential energy comes
in many forms, two of these forms are gravitational potential energy and elastic
potential energy.

Elastic Potential Energy (EPE)

The stretched rubber of a slingshot is an example of elastic potential energy. An
object that can be stretched, compressed, or twisted and tends to assume its normal
shape possesses elastic potential energy. The amount of energy that can be stored into
an object depends on how much force is applied to stretch, compress, or twist the object.
Also, on the characteristics of the elastic object. This means that the greater you stretch a
rubber band, the more elastic potential energy it will store. When you release the band,
the elastic potential energy will be released and be converted to kinetic energy as the
band tries to go back into its normal shape.

16
 Figure 3. a compressed spring Figure 4. a stretched rubber of a slingshot

Gravitational Potential Energy (GPE)

It is stored energy as a result of an objects' vertical position and mass due to the
gravitational pull of the Earth. A ball that sits at the highest point of an inclined plank and
a mango fruit that is about to fall are examples of objects that stored gravitational
potential energy.
In the experiment you conducted, you might have observed that the ball allowed
to roll in a 6 in-high plank had a different result compared to the same ball on a 12 in-high
plank. In which height did the ball store more potential energy? You answered it right if it
is on the 12 in-high plank. Which among the three balls in the experiment possessed
greater gravitational potential energy? If you answered the heaviest ball, then you are
correct. Hence, we can say that the factors which affect the gravitational potential energy
are the mass and the height of an object.

MASS: HEIGHT:
- The greater the mass of an object, - The greater the vertical position of an
the greater the gravitational potential object, the greater the gravitational
energy it stores. potential energy it possesses.

Mathematically, kinetic energy can be expressed using this equation:

Where:
GPE = mgh GPE – Gravitational Potential Energy
m – the mass of the object
What is the SI unit used to g - acceleration due to gravity
describe energy? Right! It is Joule (J). h – the height of the object

On the other hand, the mass uses kilogram (kg) and the height uses meter (m). The
acceleration due to gravity has a constant value of 9.8 .

TRICK STOP!
 Acceleration due to gravity, 9.8 , is always a given in solving for GPE.
 When the given has a different unit, always find a way to convert it first.
 Always examine the given to know which formula you should use.

17
 Let us try to solve the gravitational
potential energy of the ball before it was
released in the experiment you did earlier.
Suppose that the ball number 1 has a mass
of 0.20 kg and is positioned at a height of 6
in or 0.15 m. How much is the gravitational
potential energy it has? Figure 1: a ball placed at the highest
point of an inclined plank
Step 1: Identify the given and what is missing in the problem.
g = 9.8 m = 0.20 kg h = 0.15 m (converted 6 in) GPE = ?

Step 2: Substitute the identified given value to the formula.

Formula: GPE = mgh GPE = (0.20 kg)(9.8 )(0.15 m)

Step 3: Multiply the mass to the acceleration due to gravity and then to height to get
the value of GPE. GPE = 0.29 kg ·m or 0.29 J

Let us now try to see the gravitational potential energy of ball number 1 at a height
of 12 in or 0.30 m.
Step 1: Identify the given and what is missing in the problem.
g = 9.8 m = 0.20 kg h = 0.30 m (converted 12 in) GPE = ?
Step 2: Substitute the identified given value to the formula.
Formula: GPE = mgh GPE = (0.20 kg)(9.8 )(0.30 m)
Step 3: Multiply the mass to the acceleration due to gravity and then to height to get
the value of GPE. GPE = 0.59 kg ·m or 0.59 J

What have you observed with the result of ball number 1 at a different height? It
clearly shows how the vertical position can affect the gravitational potential energy of an
object. But what if the height of the object is 0 m, what would be its GPE?

PRACTICE IT!
What if the mass of the ball was changed from 0.20 kg to 0.80 kg at a height of 0.15 m,
will there be a change in gravitational potential energy?

Lesson 3: Maximizing the POWER!

You might remember that in the lesson of work, climbing stairs was an example of
doing work. Also, it showed how energy was used to do work. But how were energy and
work related to what we know as power?
Just like work and energy, power is defined differently in Science. It is related to
how fast work is being done or how fast energy is being used. Specifically, power is
defined as the rate of work done or the rate of using energy. Hence, we can say that
one is powerful when he or she has done work or used energy in a short amount of time.
18
 POWER on!
Analyze the given data presented in the table. Supply the missing data in the table
and answer the guide questions. Do these in a separate sheet of paper.

Name Force Height of Work Done Time taken Power (W)

(N) Stairs (m) (J) (s)
First Race
Pepay 47 4 10 18.8
Popoy 42 4 5 33.6
Second Race
Pepay 47 4 5 37.6
Popoy 42 4 5 33.6
Third Race
Pepay 47 4 5 37.6
Popoy 42 4 10 16.8
Questions:
1. Who did most of the work based on the table? What do you think is the cause of the
work difference?
2. In the first race, who reached the top of the stairs first? How about the second and
third races? Why?
3. Based on the table, who has the highest power output in the first race? Second race?
Third race?
4. Who has the lowest power output in the first race? Second race? Third race?
5. What factor/s do you think influenced the power output in the races?
In our earlier lesson about work, you might have recalled that the greater the force
applied, the greater the work will be done. You might have noticed this in the activity you
did earlier, where Pepay has done more work than Popoy. This is because the weight of
Pepay is greater than Popoy. Therefore, she needed to exert more force to lift herself than
her brother.
You might have noticed that the same work can be done quickly or slowly. Just
look at how Pepay’s work done under 5 s and 10 s. The time doesn't affect the magnitude
of work. However, a work done quickly yields a greater output of power and a work that is
done slowly makes the power output lesser. If you will compare the power output of
Popoy in 5 s and 10 s, you will see a big difference between the two. This shows you the
relationship of time to power.
Now, how do we get the amount of power for every work done or energy used?
Mathematically, we can express power through the
equation; Where:
P – Power output
W – Amount of work done
P= or P= E - Amount of energy used
t – Time taken

What is the SI unit used to describe power? It is joule per second ( ) or watt (W).
The unit watt was named in honor of James Watt, the inventor who worked on the
Improvement of the steam engine. The unit for work and energy is joule (J) and time
uses seconds (s).

19
 Aside from and W, there are other units related to power, and these are:

1 joule per second ( ) = 1 watt (W) 1 000 watt (W) = 1 kilowatt (kW)

1 horsepower (hp) = 746 watts (W)

*Horsepower is not an SI unit. It is mostly used to describe the power of an engine.

TRICK STOP!
Before you proceed in calculating, remember that it is important
to use the appropriate formula for a problem. Let us use the pie
formula chart in determining the correct formula to use. Let us say
work or energy is missing in the problem, the formula will be used is
W = Pt or E = Pt.

Let us try to calculate if the given magnitude of power in the activity you did earlier
is correct. So in the first race, Pepay’s work is 188 J and the time taken is 10 s.

Step 1: Identify the given and what is missing in the

problem.
W = 188 J t = 10 s P=?
Step 2: Use the pie formula trick to determine the
appropriate formula.
P=
Step 3: Substitute the identified given to the formula.
P=
Step 4: Apply the operation required in the formula to get the answer.
P = 18.8 or 18.8 W

Let us now try to determine the amount of work done by Popoy in the first race if the
amount of power is 33.6 and the time taken is 5 s.

Step 1: Identify the given and what is missing in

the problem.
W=? t=5s P = 33.6
Step 2: Use the pie formula trick to determine the
appropriate formula.
W = Pt
Step 3: Substitute the identified given to the
formula.
W = (33.6 )(5 s)
Step 4: Apply the operation required in the formula to get the answer.
W = (33.6 )(5 s) *Don’t forget to cancel out W = 336 J
the unit of seconds

Now try to compute for the rest of the race to see if your answers in the given table
are correct.

20
 What’s More

INDEPENDENT ACTIVITY 1
WORK
Read each problem carefully and complete the missing value in each of the steps
to solve the problem. Write your answer in a separate sheet of paper
Problem 1: How much of work is done if Popoy lifted a squash about 2 meters high with a
force of 50N?
Step 1: Identify the given and what is Step 2: Use the pie formula trick to
missing in the problem. determine the appropriate formula.
W= ? F = _______ d = 1.5 m W = ________
Step 3: Substitute the identified given to the Step 4: Apply the operation required in
formula. the formula to get the answer.
W = ( ______ ) (1.5 m ) W = ____ N·m or ______ J
Problem 2: How much force is needed for a mango fruit to fall at a height of 11 meters if
the work done by Earth is 27J?
Step 1: Identify the given and what is Step 2: Use the pie formula trick to
missing in the problem. determine the appropriate formula.
W= _____ F = ______ d = 11 m F = ______

Step 3: Substitute the identified given to Step 4: Apply the operation required in the
the formula. formula to get the answer.
N·m
F = ________ F = _______ N
m
Problem 3: A 7.5 N clay pot drops from a window sill. If the clay pot exerted 45 N·m of
work, how high is the window?
Step 1: Identify the given and what is Step 2: Use the pie formula trick to
missing in the problem. determine the appropriate formula.
W= _____ F = _____ d = ______ d = ______

Step 3: Substitute the identified given to Step 4: Apply the operation required in the
the formula. formula to get the answer.
N·m
d= ____________ d = _______m
N
INDEPENDENT ASSESSMENT 1
WORK
Analyze the given data and illustrations and solve the problem. Do these in a
separate sheet of paper.
1. Suppose that Popoy throws a stone with a force of 10 N that resulted in a 220 J of
work. How far will the stoneatravel?

21
 Solution:

2. To reach the top of the stairs with a height of 4 m, Pepay must do a work of 980 J.
How much force is needed to do this?

Solution:

INDEPENDENT ACTIVITY 2
ENERGY
A. Fill in the blanks with the correct word to describe potential or kinetic energy.
Write it in a separate sheet of paper.

Potential Energy
It is _________(motion, stored) energy of an object that depends on its _______
(mass, speed) and _____(position, time). An increase in _______(mass, speed) and
_______(direction, height) of an object will also ______ (decrease, increase) its energy.

Kinetic Energy
It is an energy in _________(motion, stored) . It is greatly affected by ______
(height, mass) and _________(position, speed) .

B. Read each problem carefully and complete the missing value in each of the
steps to solve the problem. Answer it in a separate sheet of paper.
Problem 1: A diesel-powered soil tiller has a weight 400 kg is plowing at a speed of 3 .
How much kinetic energy does the tiller have?

Step 1: Identify the given and what is Step 2: Substitute the identified given
missing in the problem. value to the formula.
m= _____ v= 3 KE = ? KE = (0.5)( _____)(3 )2
Step 3: Square the value of speed and its Step 4: Multiply the speed to the mass
unit. and then to 0.5 to get the value of KE.
KE = (0.5)(____)(____ ) KE = _____kg or ____ J

22
 Problem 2: A 3 kg-clay pot is placed at a height of 6 m. How much gravitational potential
energy is stored in the pot?
Step 1: Identify the given and what is missing in the problem .
g = 9.8 m = 3 kg h = _______ GPE = ?
Step 2: Substitute the identified given value to the formula.
GPE = (3 kg)(9.8 )( ______)

Step 3: Multiply the mass to the acceleration due to gravity and then to height to get the
value of GPE.
GPE = _______ kg ·m or ______ J

INDEPENDENT ASSESSMENT 2
ENERGY
A. Copy and complete the concept map of energy below in a separate sheet of
paper.

ENERGY

describes as

has two

describes as describes as
has two

depends on
depends on

B. Solve the following problems by analyzing the given data. Write your answer in a
separate sheet of paper.
1. Suppose that Popoy throws a 0.15 kg stone and traveled with a speed of 13 before
it hits the guava fruit. How much kinetic energy the stone had?

Solution:

13

23
2. Mango fruit is about to fall from a height of 23 m has a mass of 0.33 kg . Calculate
the gravitational potential energy of the mango fruit before it falls to the ground.

Solution:

23 m

INDEPENDENT ACTIVITY 3
POWER
Read each problem carefully and complete the missing value in each of the steps
to solve the problem. Answer it in a separate sheet of paper.

Problem 1: Suppose that Popoy did a 100 J of work in lifting the squash in 2 s. How
much of power output did Popoy have?

Step 1: Identify the given and what is Step 2: Use the pie formula trick to
missing in the problem. determine the appropriate formula.
W= _____ t= 2s P= ? P = ______
Step 3: Substitute the identified given to Step 4: Apply the operation required in the
the formula. P = ______J formula to get the answer.
s P = ______ or ____ W

Problem 2: A diesel-powered soil tiller has a power output of 8 952 is running in the
field. How much work does the tiller will do in 2 s?
Step 1: Identify the given and what is Step 2: Use the pie formula trick to
missing in the problem. determine the appropriate formula.
W= ? t= 2s P = _____ W = _______
Step 3: Substitute the identified given to Step 4: Apply the operation required in the
the formula. formula to get the answer.
W = ( ____ )(2 s) W = ________ J

Problem 3: A clay pot drops from a window sill and exerted a work of 45 J to the ground.
How long does it take for the pot to fall if its power output is 15 ?
Step 1: Identify the given and what is Step 2: Use the pie formula trick to
missing in the problem. determine the appropriate formula.
W= 45 J t = ______ P = _______ t = ______
Step 3: Substitute the identified given to Step 4: Apply the operation required in the
J
the formula. t = ______ formula to get the answer.
t = _____s

24
INDEPENDENT ASSESSMENT 3
POWER
Analyze the given data and illustrations and solve the problem. Answer them in a
separate sheet of paper.
1. Suppose that Popoy throws a stone that resulted in a 220 J of work. How much
power rating will he have in 1.5 s?

Solution:

2. If the stone thrown by Popoy has a power of 4.2 in 3 s before it hits the guava fruit,
how much kinetic energy the stone had?

Solution:

What I Have Learned

Share your thoughts on our lessons by answering the following question in a

separate sheet of paper.

1. What are the things you need to consider for work to happen? What are the learnings
you have gained in calculating work?
______________________________________________________________________
______________________________________________________________________
2. What are the differences between potential energy and kinetic energy that you have
learned from the lesson?
______________________________________________________________________
______________________________________________________________________
3. What are your insights on how mass, speed, and position affect the energy
possessed an object?
______________________________________________________________________
______________________________________________________________________
4. What are the factors that affect power? What are the learnings you have gained in
calculating power?
______________________________________________________________________
______________________________________________________________________

25
 What I Can Do

Read the situation carefully. Analyze the problem discussed in the situation and
write a short paragraph containing your suggestions on the problem. Support
your suggestions by facts you have learned about work, energy and power. The
paragraph must contain 50-100 words. A rubric will be used to rate your work. Do
this in a separate sheet of paper.
Situation: An energy generating company would like to establish a run-off-river
hydroelectric power plant in the existing dams in the province of Mapayapa. This type
of facility works through redirecting river water flow through canals and feeding it
downhill to a power station. At present, there are two dams situated in the
mountainous terrain of Mapayapa and these are Kapayapaan Dam and Kabutihan
Dam. Kapayapaan Dam has a height of 85 meters above sea level (masl). While the
Kabutihan Dam has a height of 125 masl. For the run-off-river power plant to produce
greater electric power, engineers must consider the gravitational potential energy
possess by the dams. This energy should be enough to be converted into kinetic
energy that will be used to turn the turbine at the powerhouse. They have to consider
the location of the dam and where to build the powerhouse. If you were to be a
member of the company that handles this project, what will be your suggestions?
Which of the two dams will be ideal for the project and why?
Rubrics for Run-Off-River Hydroelectric Power Plant Project Suggestion
Criteria 5 3 1
Suggestion The given
The given suggestions
suggestions are well The given
are developed with
developed with suggestions are
limited details
relevant details not developed.
supporting it.
supporting it.
Explanation Concise and clear Explanation and Little to no
and explanation and analysis of the explanation and
Analysis analysis of the situation are somehow analysis can be
situation are evident concise and clear in seen in the
in the paragraph. the paragraph. paragraph.
Mechanics There are distract-
There are errors in the
(spelling There is careful editing ing mechanics all
mechanics that are
and in the mechanics. throughout the
distracting at times.
grammar) paragraph.

Assessment

Choose the best answer for each question. Write your answer in a separate sheet of
paper.
1. How much work is done by Popoy when he pushed their dining table with a constant
force of 140 N across a distance of 3.5 meters?
A. 400 J B. 440 J C. 490 J D. 495 J

26
2. Which of the following is not a condition for work to happen?
A. A force is acting on the object.
B. The object has a definite displacement.
C. The direction of the force is the same as the direction of the motion.
D. The direction of the force is perpendicular to the direction of the motion.

3. Pepay did 300 J of work in lifting the potted plant from the floor up to the wooden
platform. If the height of the platform is 1 m, how much energy did she use to do
this?
A. 150 J B. 200 J C. 250 J D. 300 J
4. Which of the following factors affect the kinetic energy of an object?
A. acceleration due to gravity C. mass
B. height D. speed
5. What is the pigeon’s kinetic energy if it flies at a constant speed of 10 with a mass of
0.50 kg?
A. 20 J B. 25 J C. 30 J D. 35 J

6. How much potential energy is in a 50 kg box that has to be lifted to a height of 2 m?

A. 800 J B. 880 J C. 900 J D. 980 J
7. Which of the following situations applied lesser work?
A. Popoy lifted a basket of vegetables into the table.
B. Tatay Pedro pulled a sack of rice at a 45° angle.
C. Pepay pushed the bed at the corner of the room
D. A mango fruit fell on the ground.
8. In the given situations, which shows work done scientifically?
A. A driver pushed his tricycle at a distance of 5 m.
B. A white bird walked in the rice field with fish on its beak.
C. A boy pushed a big box that doesn’t moved.
D. A vendor carried a bilao of vegetable around the barangay.
9. The two runners with the same mass but has different speed are moving along the
race track. Which of the runners has more kinetic energy?
A. the runner with a lesser speed C. both runners
B. the runner with a greater speed D. neither of the runners

10. Which of the following situations has kinetic energy?

A. A stone that falls from the cliff C. A slingshot that is stretched
B. A jackfruit that hangs on its branch D. A ball that sits at the corner
11. If the guava and watermelon will fall from the same height, which of the two will have
lesser potential energy?
A. guava C. both guava and watermelon
B. watermelon D. none of the fruits

27
12. Pepay did 400 J of work in lifting the potted plant from the floor up to the wooden
platform. If she had this in 5 s, how much power did she use?
A. 80 J B. 90 KW C. 90 N D. 80 W

13. Which of the following situations has greater power output?

A. A car stops with 40 000 J of work in 20 s.
B. Mang Pilo’s has a 11 190 W soil tiller.
C. A motor stops in 2 s with 4 000 J of work.
D. A stone was thrown with an energy of 300 J and hits the ground in 2 s.

14. Tatay Pedro’s delivery truck has a power rating of 35,000 W. How much work it can
do in 2 s?
A. 70 000 J B. 75 000 J C. 80 000 J D. 85 000 J

15. The two boys with different weights climbed the same stairs and arrived at the top at
same time. Which of the following conclusions best fit the situation?

A. They both did the same amount of work and used the same power.
B. They did a different amount of work but used the same power.
C. They did the same amount of work but used different power.
D. They both did a different amount of work and power.

Additional Activities

Read each situation carefully and solve the problem. Answer it in a separate sheet
of paper and show your solution.
1. Since the rainy season has already begun, it is time for Tatay Pedro to get ready in
planting rice in the field. To do this, he must prepare the rice seed for sowing by
soaking the rice grain in the water. Tatay Pedro started pulling a sack of rice with a
force of 500 N at a distance of 10 m to get to the water irrigation site. How much work
did Tatay Pedro do?
2. Around 5:00 in the morning, the 75 kg Tatay Pedro and the 42 kg Popoy decided to
jog around the sitio after the lockdown has been lifted. Before they left the house,
both of them made sure that they were properly protected. Suppose that they jogged
at the same speed of 3 , who among them had the greater kinetic energy? Prove
your guess by providing your solution.
3. Pepay and Popoy would like to test your understanding of gravitational potential
energy. Popoy, a 42 kg boy, decided to climb a mango tree with a height of 3.5 m.
While Pepay, a 47 kg girl, decided to climb their stairs at a height of 2 m. Who among
the siblings stores greater potential energy? Prove your guess by providing your
solution.
4. While cleaning their backyard, Nanay Perla asked Pepay and Popoy to get several
pails of water for the plants. Pepay and Popoy raced towards the water pump. Popoy
did a work of 462 J to reach the place in 7 s while Pepay did a 517 J of work in 12 s.
Who exerts more power between the two? Prove your answer by providing your
solution.
28
 29
What I Know 4. The heavier ball moved the box farther
because of its mass and speed.
1. D 4. D 7. B 10. A 13. D 5. The heavier ball possessed greater energy
2. B 5. C 8. A 11. A 14.B because it exerts more work than the lighter ball.
3. B 6. C 9. A 12. D 15. C 6. Yes. The increase in height caused the balls to
roll faster than in 6-in high plank.
Lesson 1: Making it WORK 7. A greater mass and height causes for it to do
What’s the LAW? greater work which is equal to a greater energy
1. Inertia 4. Interaction used.
2. Interaction 5. Inertia Lesson 3: Maximizing POWER!
3. Acceleration POWER on!
A. WORK on it!
1: Pepay did most of the work.
2: Because Pepay was able to push the cart
farther than Popoy.
B. WORK on this!
Action taken Did you If yes
apply Direction Direction
force? of the of the
Force movement
Lifting the Yes upward upward
book Questions
Pushing the Yes forward forward 1. Pepay did more work than Popoy because the
book force exerted by Pepay was greater.
2. In the first race, Popoy came first because it takes
Putting it Together!
him only 5 s to reach the top. In the second race,
In order for work to happen, there must be both reached the top at 5 s. in the third race, Pepay
a force and a displacement. However, there will came first because she reached the top faster than
be no work done if the force applied does not Popoy.
cause any movement. Work is considered done if 3. First race: Popoy Second race: Pepay Third
the direction of the force is same with the dis- Race Pepay
placement. Hence, there is no work when a force 4. First race: Pepay Second race: Popoy Third
is applied perpendicular to the displacement. Race: Popoy
5. time and work
Lesson 3: Working with ENERGY! Independent Activity 1
Experiment 1 Problem 1
*Answer on the table may vary depending on the
actual result of the experiment. A sample table is
provided.
Height of the Distance moved by the box (inch)
inclined plank
Ball Ball Ball
number number number Problem 2
1 2 3
At 6 inches 7 14 20
At 12 inches 20 30 50
Questions:
1: Yes, I did work on the ball by pushing it lightly which Problem 3
made the ball roll and eventually did work on the box.
2. There was energy when the ball rolled on the plank
and when it hit the box. Because the ball was able to
do work on the box.
3. No, there will be no work or energy in the
situation. An absence of work means no energy has
been used.
Answer Key
 30
Independent Assessment 1 Independent Activity 3
Problem 1 Problem 2
Problem 3
Independent Activity 2
A. Potential Energy
It is stored energy of an object that depends on its
mass and position. An increase in mass and height
of an object will also increase its energy.
Kinetic Energy Independent Assessment 3
It is an energy in motion. It is greatly affected by
speed and mass.
B. Problem 1
Assessment
1. C 4. D 7. B 10. A 13. B
2. D 5. B 8. A 11. A 14. A
3. D 6. D 9. B 12. D 15. D
Problem 2
Additional Activities
1.
Independent Assessment 2 2. Tatay Pedro has more kinetic energy.
A.
3. Popoy stored more gravitational potential energy
than Pepay.
4. Popoy exerted more power than Pepay.
B.
Answer Key
 References

Department of Education. EASE/OSHP Module 11: Work, Energy,Power, and Machines.

Philippines: Department of Education. 2014.
Messa, Gideon, and Vincent Kapui. Grade 11 Physics Module 4: Work, Power and
Energy. Papua New Guinea: Flexible Open and Distance Education. 2017.
https://fode.education.gov.pg/courses/Science/Grade%2011/physics/
Grade.11.Physics.Module4.pdf.
Padua, Alicia L., and Ricardo M. Crisostomo. Practical and Explorational Physics:
Modular Approach. Quezon City: Vibal Publishing House. 2003.
Rabago, Lilia M., Alvin C. Flores, Thelma R. Mingoa, Diana L. Ferrer, Eligio C. Obille, Jr.,
and Miguel C. Cano. Dynamic Science: An Integration of Physical and Biological
Sciences: Modular Approach. Quezon City: Vibal Publishing House. 2003.
Rabago, Lilia M., Maria Jessica B Alumaga, Echel Simon-Antero, Crescencia C. Joaquin,
Catherine Genevieve B. Lagunzad, Ricardo M. Crisostomo, Alicia L. Padua,
Maria Carmela A. Boncodin, Thelma R. Mingoa, and Micahel A. Toledo. Science
and Technology 8. Quezon City: Vibal Publishing House. 2014.
The Physics Classroom. “Power.” Accessed July 12, 2020.
https://www.physicsclassroom.com/class/energy/Lesson-1/Power.

31
 For inquiries or feedback, please write or call:
Department of Education, Schools Division of Bulacan
Curriculum Implementation Division
Learning Resource Management and Development System (LRMDS)
Capitol Compound, Guinhawa St., City of Malolos, Bulacan
Email address: lrmdsbulacan@deped.gov.ph