GRADE 8: WORK, POWER AND ENERGY
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Work, Energy, and Power are fundamental concepts of Physics. Work is an abstract concept in physics that is connected to energy. When work is completed, there is a change of energy. When work is done by an object, it loses energy, and when work is done on an object it gains energy. Doesn't it seem confusing? Don't worry; as you go through this material, it will become evident to you what the work is intended for. If you loved learning about motion, you will be more inspired to study physics in this section.
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Work has a lot of definitions for individuals. You commonly know that work is doing something like eating, sleeping, writing, or doing jobs such as teaching, cooking, and much more. But did you know what work is in physics? In this section, you will understand the concepts of work, power, and energy to understand how things are done and are not done. Work, energy, and power are highly inter-related concepts that come up regularly in everyday life. You do work on an object when you move it. The rate at which you do the work is your power output. When you do work on an object, you transfer energy from one object to another.
A child pushes the sleigh upward with a 60 Newton and a distance of 10 meters. How much work did the child do on a sleigh?
Given:
F= 60 Newton
d= 10 meters
W= 60 N x 10 m
W= 600 J
A child pushes the sleigh upward with a 75 Newton and a distance of 10 meters. How much work did the child do on a sleigh?
Given:
F= 75 Newton
d= 10 meters
W= 75 N x 10 m
W= 750 J
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How much work is done if Peter applies 55 Newton to lift the box from the floor with a height of 1 meter?
Given:
F= 55 Newton
d= 1 meter
W= 55 N x 1 m
W = 55 J
How much work is done if Peter applies 55 Newton to lift the box from the floor with a height of 2 meters?
Given:
F= 55 Newton
d= 2 meter
W= 55 N x 2 m
W = 110 J
POTENTIAL ENERGY
is attributed to mass and position.
A ball on the top of a hill.
vs.
vs.
KINETIC ENERGY
is associated with mass and speed.
A ball rolls down a hill.
A ball at the top of a hill has potential energy due to its position. When the ball rolls down the hill. The rolling ball has kinetic energy. Thus, the potential energy stored in the ball in its current position changes into kinetic energy when the ball rolls.
POTENTIAL ENERGY
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KINETIC ENERGY
Explore how kinetic energy and potential energy work using the PhET Interactive Simulation
Speed and energy have an inverse connection. It is reasonable to assume that the faster anything moves, the more energy it possesses. Greater levels of energy will cause a more significant change in motion for the item on which it is operating. When the speed of an item decreases, so does the distance it travels.
A soccer player kicks the ball with 46 Newton passing to other teammates with a speed of 5 seconds with 20 meters away. How much power does the soccer player apply?
Given: F= 46 Newton
d= 20 meters
t= 5 seconds
To get the value of work, multiply force by distance.
W= 46 N x 20 m
W = 920 Joules
After getting the value of work, compute the value of power.
P= 920 Joules / 5 seconds
P= 184 J/s
A soccer player kicks the ball with 55 Newton passing to other teammates with a speed of 5 seconds with 20 meters away. How much power does the soccer player apply?
Given: F= 55 Newton
d= 20 meters
t= 5 seconds
To get the value of work, multiply force by distance.
W= 55 N x 20 m
W = 1100 Joules
After getting the value of work, compute the value of power.
P= 1100 Joules / 5 seconds
P= 220 J/s
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What is the power of a train that does 6000 J of work in 62 seconds?
Given:
W= 6000 Joules
t= 62 seconds
P= 6000 Joules / 62 seconds
P= 96.77 J/s
What is the power of a train that does 6000 J of work in 50 seconds?
Given:
W= 6000 Joules
t= 50 seconds
P= 6000 Joules / 50 seconds
P= 120 J/s
Power is then directly proportional to the work done and inversely proportional to the time to do the work. The work done increases the power also increases.
Energy is the ability to do work. Power is defined as the efficiency with which a task is completed. As a result, tasks cannot be completed without energy or efficiency. Hence, work, energy, and power are all related to one another. The force exerted on an object over a distance does work. Work can increase energy, and energy can do work. Power is the rate at which work is done. What is the Relation Between Work and Energy? Energy must be transferred to an object to help it move, and the energy can be transferred in the form of force. The energy transferred by force to move any object is known as work or work done. Therefore, work and energy have a direct relationship.
WORK IS DONE
Examples:
A man pulling a 1/2 sack of corn and moving it from North to South.
A pitcher throws a baseball to a batter or hitter.
The children mold different shapes using clay.
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NO WORK IS DONE
Examples:
A kid holding a glass of milk.
Explanation- A glass of milk does not move (in the direction of force applied there is no displacement).
The vendor carrying a basket at a constant speed.
Explanation- In the direction there's no net force.
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Energy Skate Park. (2020). Colorado.edu. https://phet.colorado.edu/sims/html/energy-skate-park/latest/energy-skate-park_all.html
The Learning Bees. (2020a, November 1). Work and Energy | Grade 8 Science DepEd MELC-Based Quarter 1 Module 3 Part 1 Work [Video]. YouTube. https://www.youtube.com/watch?v=gv4cshx8Khg
The Learning Bees. (2020, November 5). Work and Energy | Grade 8 Science DepEd MELC Quarter 1 Module 3 Part 2 Potential Energy [Video]. YouTube. https://www.youtube.com/watch?v=nRxFn5dq7h0
The Learning Bees. (2020c, November 7). Work and Energy | Grade 8 Science DepEd MELC Quarter 1 Module 3 Part 3 Kinetic Energy [Video]. YouTube. https://www.youtube.com/watch?v=JGBQM0DHgTI
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