## 9.1 Work, Power, and the Work–Energy Theorem

Section learning objectives.

By the end of this section, you will be able to do the following:

- Describe and apply the work–energy theorem
- Describe and calculate work and power

## Teacher Support

The learning objectives in this section will help your students master the following standards:

- (A) describe and apply the work–energy theorem;
- (C) describe and calculate work and power.

In addition, the High School Physics Laboratory Manual addresses the following standards:

- (C) calculate the mechanical energy of, power generated within, impulse applied to, and momentum of a physical system.

Use the lab titled Work and Energy as a supplement to address content in this section.

## Section Key Terms

In this section, students learn how work determines changes in kinetic energy and that power is the rate at which work is done.

[BL] [OL] Review understanding of mass, velocity, and acceleration due to gravity. Define the general definitions of the words potential and kinetic .

[AL] [AL] Remind students of the equation W = P E e = f m g W = P E e = f m g . Point out that acceleration due to gravity is a constant, therefore PE e that results from work done by gravity will also be constant. Compare this to acceleration due to other forces, such as applying muscles to lift a rock, which may not be constant.

## The Work–Energy Theorem

In physics, the term work has a very specific definition. Work is application of force, f f , to move an object over a distance, d , in the direction that the force is applied. Work, W , is described by the equation

Some things that we typically consider to be work are not work in the scientific sense of the term. Let’s consider a few examples. Think about why each of the following statements is true.

- Homework is not work.
- Lifting a rock upwards off the ground is work.
- Carrying a rock in a straight path across the lawn at a constant speed is not work.

The first two examples are fairly simple. Homework is not work because objects are not being moved over a distance. Lifting a rock up off the ground is work because the rock is moving in the direction that force is applied. The last example is less obvious. Recall from the laws of motion that force is not required to move an object at constant velocity. Therefore, while some force may be applied to keep the rock up off the ground, no net force is applied to keep the rock moving forward at constant velocity.

[BL] [OL] Explain that, when this theorem is applied to an object that is initially at rest and then accelerates, the 1 2 m v 1 2 1 2 m v 1 2 term equals zero.

[OL] [AL] Work is measured in joules and W = f d W = f d . Force is measured in newtons and distance in meters, so joules are equivalent to newton-meters ( N ⋅ m ) ( N ⋅ m )

Work and energy are closely related. When you do work to move an object, you change the object’s energy. You (or an object) also expend energy to do work. In fact, energy can be defined as the ability to do work. Energy can take a variety of different forms, and one form of energy can transform to another. In this chapter we will be concerned with mechanical energy , which comes in two forms: kinetic energy and potential energy .

- Kinetic energy is also called energy of motion. A moving object has kinetic energy.
- Potential energy, sometimes called stored energy, comes in several forms. Gravitational potential energy is the stored energy an object has as a result of its position above Earth’s surface (or another object in space). A roller coaster car at the top of a hill has gravitational potential energy.

Let’s examine how doing work on an object changes the object’s energy. If we apply force to lift a rock off the ground, we increase the rock’s potential energy, PE . If we drop the rock, the force of gravity increases the rock’s kinetic energy as the rock moves downward until it hits the ground.

The force we exert to lift the rock is equal to its weight, w , which is equal to its mass, m , multiplied by acceleration due to gravity, g .

The work we do on the rock equals the force we exert multiplied by the distance, d , that we lift the rock. The work we do on the rock also equals the rock’s gain in gravitational potential energy, PE e .

Kinetic energy depends on the mass of an object and its velocity, v .

When we drop the rock the force of gravity causes the rock to fall, giving the rock kinetic energy. When work done on an object increases only its kinetic energy, then the net work equals the change in the value of the quantity 1 2 m v 2 1 2 m v 2 . This is a statement of the work–energy theorem , which is expressed mathematically as

The subscripts 2 and 1 indicate the final and initial velocity, respectively. This theorem was proposed and successfully tested by James Joule, shown in Figure 9.2 .

Does the name Joule sound familiar? The joule (J) is the metric unit of measurement for both work and energy. The measurement of work and energy with the same unit reinforces the idea that work and energy are related and can be converted into one another. 1.0 J = 1.0 N∙m, the units of force multiplied by distance. 1.0 N = 1.0 kg∙m/s 2 , so 1.0 J = 1.0 kg∙m 2 /s 2 . Analyzing the units of the term (1/2) m v 2 will produce the same units for joules.

## Watch Physics

Work and energy.

This video explains the work energy theorem and discusses how work done on an object increases the object’s KE.

## Grasp Check

True or false—The energy increase of an object acted on only by a gravitational force is equal to the product of the object's weight and the distance the object falls.

Repeat the information on kinetic and potential energy discussed earlier in the section. Have the students distinguish between and understand the two ways of increasing the energy of an object (1) applying a horizontal force to increase KE and (2) applying a vertical force to increase PE.

## Calculations Involving Work and Power

In applications that involve work, we are often interested in how fast the work is done. For example, in roller coaster design, the amount of time it takes to lift a roller coaster car to the top of the first hill is an important consideration. Taking a half hour on the ascent will surely irritate riders and decrease ticket sales. Let’s take a look at how to calculate the time it takes to do work.

Recall that a rate can be used to describe a quantity, such as work, over a period of time. Power is the rate at which work is done. In this case, rate means per unit of time . Power is calculated by dividing the work done by the time it took to do the work.

Let’s consider an example that can help illustrate the differences among work, force, and power. Suppose the woman in Figure 9.3 lifting the TV with a pulley gets the TV to the fourth floor in two minutes, and the man carrying the TV up the stairs takes five minutes to arrive at the same place. They have done the same amount of work ( f d ) ( f d ) on the TV, because they have moved the same mass over the same vertical distance, which requires the same amount of upward force. However, the woman using the pulley has generated more power. This is because she did the work in a shorter amount of time, so the denominator of the power formula, t , is smaller. (For simplicity’s sake, we will leave aside for now the fact that the man climbing the stairs has also done work on himself.)

Power can be expressed in units of watts (W). This unit can be used to measure power related to any form of energy or work. You have most likely heard the term used in relation to electrical devices, especially light bulbs. Multiplying power by time gives the amount of energy. Electricity is sold in kilowatt-hours because that equals the amount of electrical energy consumed.

The watt unit was named after James Watt (1736–1819) (see Figure 9.4 ). He was a Scottish engineer and inventor who discovered how to coax more power out of steam engines.

[BL] [OL] Review the concept that work changes the energy of an object or system. Review the units of work, energy, force, and distance. Use the equations for mechanical energy and work to show what is work and what is not. Make it clear why holding something off the ground or carrying something over a level surface is not work in the scientific sense.

[OL] Ask the students to use the mechanical energy equations to explain why each of these is or is not work. Ask them to provide more examples until they understand the difference between the scientific term work and a task that is simply difficult but not literally work (in the scientific sense).

[BL] [OL] Stress that power is a rate and that rate means "per unit of time." In the metric system this unit is usually seconds. End the section by clearing up any misconceptions about the distinctions between force, work, and power.

[AL] Explain relationships between the units for force, work, and power. If W = f d W = f d and work can be expressed in J, then P = W t = f d t P = W t = f d t so power can be expressed in units of N ⋅ m s N ⋅ m s

Also explain that we buy electricity in kilowatt-hours because, when power is multiplied by time, the time units cancel, which leaves work or energy.

## Links To Physics

Watt’s steam engine.

James Watt did not invent the steam engine, but by the time he was finished tinkering with it, it was more useful. The first steam engines were not only inefficient, they only produced a back and forth, or reciprocal , motion. This was natural because pistons move in and out as the pressure in the chamber changes. This limitation was okay for simple tasks like pumping water or mashing potatoes, but did not work so well for moving a train. Watt was able build a steam engine that converted reciprocal motion to circular motion. With that one innovation, the industrial revolution was off and running. The world would never be the same. One of Watt's steam engines is shown in Figure 9.5 . The video that follows the figure explains the importance of the steam engine in the industrial revolution.

Initiate a discussion on the historical significance of suddenly increasing the amount of power available to industries and transportation. Have students consider the fact that the speed of transportation increased roughly tenfold. Changes in how goods were manufactured were just as great. Ask students how they think the resulting changes in lifestyle compare to more recent changes brought about by innovations such as air travel and the Internet.

## Watt's Role in the Industrial Revolution

This video demonstrates how the watts that resulted from Watt's inventions helped make the industrial revolution possible and allowed England to enter a new historical era.

Which form of mechanical energy does the steam engine generate?

- Potential energy
- Kinetic energy
- Nuclear energy
- Solar energy

Before proceeding, be sure you understand the distinctions among force, work, energy, and power. 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.

## Worked Example

Applying the work–energy theorem.

An ice skater with a mass of 50 kg is gliding across the ice at a speed of 8 m/s when her friend comes up from behind and gives her a push, causing her speed to increase to 12 m/s. How much work did the friend do on the skater?

The work–energy theorem can be applied to the problem. Write the equation for the theorem and simplify it if possible.

Identify the variables. m = 50 kg,

Substitute.

Work done on an object or system increases its energy. In this case, the increase is to the skater’s kinetic energy. It follows that the increase in energy must be the difference in KE before and after the push.

## Tips For Success

This problem illustrates a general technique for approaching problems that require you to apply formulas: Identify the unknown and the known variables, express the unknown variables in terms of the known variables, and then enter all the known values.

Identify the three variables and choose the relevant equation. Distinguish between initial and final velocity and pay attention to the minus sign.

## Practice Problems

Identify which of the following actions generates more power. Show your work.

- carrying a 100 N TV to the second floor in 50 s or
- carrying a 24 N watermelon to the second floor in 10 s ?
- Carrying a 100 N TV generates more power than carrying a 24 N watermelon to the same height because power is defined as work done times the time interval.
- Carrying a 100 N TV generates more power than carrying a 24 N watermelon to the same height because power is defined as the ratio of work done to the time interval.
- Carrying a 24 N watermelon generates more power than carrying a 100 N TV to the same height because power is defined as work done times the time interval.
- Carrying a 24 N watermelon generates more power than carrying a 100 N TV to the same height because power is defined as the ratio of work done and the time interval.

## Check Your Understanding

- work and force
- energy and weight
- work and energy
- weight and force

When a coconut falls from a tree, work W is done on it as it falls to the beach. This work is described by the equation

Identify the quantities F , d , m , v 1 , and v 2 in this event.

- F is the force of gravity, which is equal to the weight of the coconut, d is the distance the nut falls, m is the mass of the earth, v 1 is the initial velocity, and v 2 is the velocity with which it hits the beach.
- F is the force of gravity, which is equal to the weight of the coconut, d is the distance the nut falls, m is the mass of the coconut, v 1 is the initial velocity, and v 2 is the velocity with which it hits the beach.
- F is the force of gravity, which is equal to the weight of the coconut, d is the distance the nut falls, m is the mass of the earth, v 1 is the velocity with which it hits the beach, and v 2 is the initial velocity.
- F is the force of gravity, which is equal to the weight of the coconut, d is the distance the nut falls, m is the mass of the coconut, v 1 is the velocity with which it hits the beach, and v 2 is the initial velocity.

Use Check Your Understanding questions to assess students’ achievement of the section’s learning objectives. If students are struggling with a specific objective, the Check Your Understanding will help identify which one and direct students to the relevant content.

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- Work Energy Power

## Work, Energy and Power

Work, Energy and Power are fundamental concepts of Physics. Work is said to be done when a force (push or pull) applied to an object causes a displacement of the object. We define the capacity to do the work as energy. Power is the work done per unit of time. This article discusses work, energy and power in detail.

## What is Work?

For work to be done, a force must be exerted and there must be motion or displacement in the direction of the force. The work done by a force acting on an object is equal to the magnitude of the force multiplied by the distance moved in the direction of the force. Work has only magnitude and no direction. Hence, work is a scalar quantity.

## Formula of Work

The work done by a force is defined to be the product of the component of the force in the direction of the displacement and the magnitude of this displacement.

Where W is the work done, F is the force, d is the displacement, θ is the angle between force and displacement and F cosθ is the component of force in the direction of displacement.

We understand from the work equation that if there is no displacement, there is no work done, irrespective of how large the force is. To summarize, we can say that no work is done if:

- the displacement is zero
- the force is zero
- the force and displacement are mutually perpendicular to each other.

## Can the work done be negative? Watch the video and find out!

## Unit of Work

The SI unit of work is Joule (J). For example, if a force of 5 newtons is applied to an object and moves 2 meters, the work done will be 10 newton-meter or 10 Joule. It should be noted that 1 J = 1 N ⋅ m = 1 kg ⋅ m 2 /s 2 .

## Example of Work

An object is horizontally dragged across the surface by a 100 N force acting parallel to the surface. Find out the amount of work done by the force in moving the object through a distance of 8 m.

F = 100 N, d = 8 m

Since F and d are in the same direction, θ = 0, [θ is the angle of the force to the direction of movement], therefore

W = FdCos θ

W = 100 x 8 x Cos 0

W = 800 J [Since Cos 0 = 1]

## Related Concepts

What is energy.

Energy is the ability to perform work. Energy can neither be created nor destroyed, and it can only be transformed from one form to another. The unit of Energy is the same as of Work, i.e. Joules. Energy is found in many things, and thus there are different types of energy.

All forms of energy are either kinetic or potential. The energy in motion is known as Kinetic Energy, whereas Potential Energy is the energy stored in an object and is measured by the amount of work done.

## Types of Energy

Some other types of energy are given below:

- Mechanical energy
- Mechanical wave energy
- Chemical energy
- Electric energy
- Magnetic energy
- Radiant energy
- Nuclear energy
- Ionization energy
- Elastic energy
- Gravitational energy
- Thermal energy
- Heat Energy

## Unit of Energy

The SI unit of energy is Joules (J), named in honour of James Prescott Joule.

## Watch the video and solve NCERT exercise questions in the chapter Work and Energy Class 9

## What is Power?

Power is a physical concept with several different meanings, depending on the context and the available information. We can define power as the rate of doing work, and it is the amount of energy consumed per unit of time.

## Formula of Power

As discussed, power is the rate of doing work. Therefore, it can be calculated by dividing work done by time. The formula for power is given below.

## Unit of Power

As power doesn’t have any direction, it is a scalar quantity. The SI unit of power is Joules per Second (J/s), which is termed as Watt. Watt can be defined as the power needed to do one joule of work in one second. The unit Watt is dedicated in honour of Sir James Watt, the developer of the steam engine.

Read the article below to learn the SI unit of power in detail.

## Example of Power

First we need to calculate the work done, which requires the force necessary to lift the truck against gravity:

F = mg = 1000 x 9.81 = 9810 N.

W = Fd = 9810N x 2m = 19620 Nm = 19620 J.

The power is P = W/t = 19620J / 15s = 1308 J/s = 1308 W.

## Related Concept

Work, power and energy questions.

- What is the relationship between work, energy and power?
- What happens to the energy as work is done?
- What is the difference between work, energy and power?
- Is energy transferred the same as work done?
- How does work affect an object’s energy?

## How are work, energy and power related to each other?

- How are force, energy and work related?
- What is the formula of work, energy and power?
- How do you calculate energy from power?
- Can force be converted into energy?

## Video Explanation of Work, Energy and Power

Here is an engaging video explanation of Work, Energy and Power and the relationship between them.

## Important Resources for Work, Energy and Power

Overview of work, energy and power, watch the video and solve complete exemplar questions in the chapter work and energy class 9.

## Frequently Asked Questions

Work is the energy needed to apply a force to move an object a particular distance. Power is the rate at which that work is done.

## What is the unit of work?

The unit of work is Joule.

## What is the unit of energy?

The unit of energy is Joule.

## What is the unit of power?

The unit of power is Watt.

## Is power a scalar quantity?

Power is a scalar quantity because it is a ratio of two scalar quantities.

Work, Power and Energy is one of the important topics of JEE Main and JEE Advanced, watch the video and understand the type of questions asked from this topic!

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## 7: Work, Energy, and Energy Resources

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There is no simple, yet accurate, scientific definition for energy. Energy is characterized by its many forms and the fact that it is conserved. We can loosely define energy as the ability to do work, admitting that in some circumstances not all energy is available to do work. Because of the association of energy with work, we begin the chapter with a discussion of work. Work is intimately related to energy and how energy moves from one system to another or changes form.

- 7.0: Prelude to Work, Energy, and Energy Resources Energy plays an essential role both in everyday events and in scientific phenomena. You can no doubt name many forms of energy, from that provided by our foods, to the energy we use to run our cars, to the sunlight that warms us on the beach. You can also cite examples of what people call energy that may not be scientific, such as someone having an energetic personality. Not only does energy have many interesting forms, it is involved in almost all phenomena, and is one of the most important con
- 7.1: Work- The Scientific Definition Work is the transfer of energy by a force acting on an object as it is displaced. The work \(W\) that a force \(F\) does on an object is the product of the magnitude \(F\) of the force, times the magnitude \(d\) of the displacement, times the cosine of the angle \(\theta\) between them. In symbols, \[W = Fd \space cos \space \theta. \] The SI unit for work and energy is the joule (J), where \(1 \space J = 1 \space N \cdot m = 1 \space kg \space m^2/s^2\). The work done by a force is zero if the
- 7.2: Kinetic Energy and the Work-Energy Theorem The net work \(W_{net}\) is the work done by the net force acting on an object. Work done on an object transfers energy to the object. The translational kinetic energy of an object of mass \(m\) moving at speed \(v\) is \(KE = \frac{1}{2}mv^2\). The work-energy theorem states that the net work \(W_{net} \) on a system changes its kinetic energy, \(W_{net} = \frac{1}{2}mv^2 - \frac{1}{2}mv_0^2\).
- 7.3: Gravitational Potential Energy Work done against gravity in lifting an object becomes potential energy of the object-Earth system. The change in gravitational potential energy \(\Delta PE_g\), is \(\Delta PE_g = mgh\), with \(h\) being the increase in height and \(g\) the acceleration due to gravity. The gravitational potential energy of an object near Earth’s surface is due to its position in the mass-Earth system. Only differences in gravitational potential energy, \(\Delta PE_g\), have physical significance. As an obje
- 7.4: Conservative Forces and Potential Energy A conservative force is one for which work depends only on the starting and ending points of a motion, not on the path taken. We can define potential energy \((PE\) for any conservative force, just as we defined \(PE_g\) for the gravitational force. The potential energy of a spring is \(PE_s = \frac{1}{2}kx^2\), where \(k\) is the spring’s force constant and |(x\) is the displacement from its undeformed position. Mechanical energy is defined to be \(KE = PE\) for conservative force.
- 7.5: Nonconservative Forces A nonconservative force is one for which work depends on the path. Friction is an example of a nonconservative force that changes mechanical energy into thermal energy. Work \(W_{nc}\) done by a nonconservative force changes the mechanical energy of a system. In equation form, \(W_{nc} = \Delta KE + \Delta PE \) or, equivalently, \(KE_i + PE_i + W_{nc} = KE_f + PE_f .\) When both conservative and nonconservative forces act, energy conservation can be applied and used to calculate motion in terms
- 7.6: Conservation of Energy The law of conservation of energy states that the total energy is constant in any process. Energy may change in form or be transferred from one system to another, but the total remains the same. When all forms of energy are considered, conservation of energy is written in equation form as \[KE_i + PE_i + W_{nc} + OE_i = KE_f + PE_f + OE_f ,\] where \(OE\) is all other forms of energy besides mechanical energy.
- 7.7: Power Power is the rate at which work is done, or in equation form, for the average power \(P\) for work \(W\) done over a time \(t\), \(P = W/t\). The SI unit for power is the watt (W), where \(1 \space W = 1 \space J/s\). The power of many devices such as electric motors is also often expressed in horsepower (hp), where \(1\space hp = 746 \space W.\)
- 7.8: Work, Energy, and Power in Humans The human body converts energy stored in food into work, thermal energy, and/or chemical energy that is stored in fatty tissue. The rate at which the body uses food energy to sustain life and to do different activities is called the metabolic rate, and the corresponding rate when at rest is called the basal metabolic rate (BMR) The energy included in the basal metabolic rate is divided among various systems in the body, with the largest fraction going to the liver and spleen, and the brain.
- 7.9: World Energy Use The relative use of different fuels to provide energy has changed over the years, but fuel use is currently dominated by oil, although natural gas and solar contributions are increasing. Although non-renewable sources dominate, some countries meet a sizeable percentage of their electricity needs from renewable resources. The United States obtains only about 10% of its energy from renewable sources, mostly hydroelectric power.
- 7.E: Work, Energy, and Energy Resources (Exercise)

Thumbnail: One form of energy is mechanical work, the energy required to move an object of mass m a distance d when opposed by a force F, such as gravity. Image use with permission (CC-SA-BY-NC -3.0; anonymous).

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## AP Physics 1 : Work, Energy, and Power

Study concepts, example questions & explanations for ap physics 1, all ap physics 1 resources, example questions, example question #1 : work, energy, and power.

None of the other answers here

The most important part of this question is noticing that it asks how much work has been done on the bar, not how much work the bodybuilder has exerted. Therefore we can use the work energy theorem:

Since the bar is initially at rest and returns to rest, the net work on the bar is zero. All of the energy exerted by the bodybuilder is counteracted by gravity.

Think about the system practically. Comparing the initial and final states, the bar is in the exact same position.

Since the truck is traveling at a constant rate, we know that all of the power exerted by the truck is going into a gain in potential energy. The power exerted will be a function of the change in potential energy over time. Therefore, we can write the following formula:

We can substitute velocity into this equation:

We have values for all of these variables, allowing us to solve:

## Example Question #3 : Work, Energy, And Power

## Example Question #4 : Work, Energy, And Power

Juri is tugging her wagon behind her on the way to... wherever her wagon needs to go. The wagon repair shop. She has a trek ahead of her--five kilometers--and she's pulling with a force of 200 newtons. If she's pulling at an angle of 35 degrees to the horizontal, what work will be exerted on the wagon to get to the repair shop?

Work exerted on an object is equal to the dot product of the force and displacement vectors, or the product of the magnitudes of the vectors and the sin of the angle between them:

The work exerted on the wagon in this problem is thus:

## Example Question #1 : Newtonian Mechanics

Since this question refers to work done by nonconservative forces, we know that:

In our case:

## Example Question #6 : Work, Energy, And Power

The work done by a centripetal force on an object moving in a circle at constant speed is __________ .

equal to the force exerted

equal to the kinetic energy of the object

equal to the force exerted multiplied by the displacement

Recall that work can be defined as:

## Example Question #7 : Work, Energy, And Power

Raul is pushing a broken down car across the flat expanse of the Mojave to his shop.

If his shop is three kilometers away and he pushes with a Herculean force of one thousand newtons in the direction of his shop, how much work will be done on the car?

Work is given by the dot product of force and displacement. Since both the force and displacement are in the same direction in this problem, work is simply the product of the two:

## Example Question #8 : Work, Energy, And Power

## Example Question #9 : Work, Energy, And Power

we can use the evidence provided by the problem to solve for distance.

## Example Question #1 : Work

A 50kg man pushes against a wall with a force of 100N for 10 seconds. How much work does the man accomplish?

## Report an issue with this question

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## Physics library

Course: physics library > unit 5.

- Introduction to work and energy
- Work and energy (part 2)
- Conservation of energy

## What are energy and work?

- What is kinetic energy?
- What is gravitational potential energy?
- What is conservation of energy?
- Work and the work-energy principle
- Work as the transfer of energy
- Work example problems
- Work as area under curve
- Thermal energy from friction
- What is thermal energy?
- Work/energy problem with friction
- Conservative forces
- What is power?

## What does energy and work mean?

- A speeding bullet has a measurable amount of energy associated with it; this is known as kinetic energy . The bullet gained this energy because work was done on it by a charge of gunpowder which lost some chemical potential energy in the process.
- A hot cup of coffee has a measurable amount of thermal energy which it acquired via work done by a microwave oven, which in turn took electrical energy from the electrical grid.

## How do we measure energy and work?

How long do i have to push a heavy box around to burn off one chocolate bar, what if we aren't pushing straight on, what about lifting weights instead, what about simply holding a weight stationary, want to join the conversation.

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## Work, Energy & Power Quiz

This online quiz is intended to give you extra practice in performing a variety of calculations involving work, energy and power, including kinetic and potential energy. This quiz aligns with the following NGSS standard(s): HS-PS3-1 , HS-PS3-2

Select your preferences below and click 'Start' to give it a try!

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## Work and Energy Module

The Work and Energy module consists of 10 missions (assignments) that address such topics as work, power, kinetic and potential energy, and the relationship between the mechanical energy of an object and the work done upon or by it. The 10 missions and the corresponding objectives are listed below. Tap a mission's name to begin.

## Quick Links to Missions:

Mission objectives:.

Mission WE1: Work

- The student should be able to define work and identify its units.
- The student should be able to predict whether a force is doing positive, negative or zero work.

Mission WE2: Power

- The student should be able to define power and identify its units. The student should be able to distinguish between work and power and calculate the power for physical situations.

Mission WE3: Kinetic and Potential Energy

- The student should be able to define kinetic energy, identify the standard unit of kinetic energy and identify the variables which effect (and do not effect) the kinetic energy of an object.
- The student should be able to define potential energy, identify the standard unit of potential energy and identify the variables which effect (and do not effect) the potential energy of an object.

Mission WE4: Mechanical Energy

- The student should be able to define mechanical energy and relate it to the amount of kinetic energy and potential energy.
- The student should be able to analyze a physical situation and identify whether the total mechanical energy of an object is increasing, decreasing or remaining constant.

Mission WE5: Conservative and Non-Conservative Forces

- The student should be able to categorize forces as being conservative or non-conservative and explain the significance of such a categorization scheme.
- The student should be able to predict whether an object's total mechanical energy would be conserved or not conserved based upon the types of forces which are doing work upon the object.

Mission WE6: Energy Bar Charts

- The student should be able to utilize a bar chart and the work-energy relationship to analyze a physical situation and develop an equation which relates the energies of the initial and final states of a motion.

Mission WE7: Mechanical Energy Conservation

- The student should be able to identify the basic principles of and the conditions required for energy conservation.
- The student should be able to apply the principles of energy conservation to a variety of physical situations.

Mission WE8: Energy Analysis

- The student should be able to conduct an energy analysis to determine the kinetic and/or the potential energy of an object at a given location.
- The student should be able to conduct an energy analysis to determine the height or speed of an object at a given location.

Mission WE9: Work and Energy Conversions

- The student should be able to identify the conditions in which mechanical energy is not conserved and demonstrate an understanding of the distinction between energy conservation and non-conservation.
- The student should be able to apply the work-energy relationship to simple physical situations.

Mission WE10: Work-Energy Analysis

## IMAGES

## VIDEO

## COMMENTS

This is a statement of the work-energy theorem, which is expressed mathematically as. W = ΔKE = 1 2mv22 − 1 2mv21. W = Δ K E = 1 2 m v 2 2 − 1 2 m v 1 2. The subscripts 2 and 1 indicate the final and initial velocity, respectively. This theorem was proposed and successfully tested by James Joule, shown in Figure 9.2.

The unit for power is a watt, which is a joule per second., A force of 75 N at an angle of 15° to the direction of motion moves a chair 3 m. Which change would result in more work being done on the chair? using 60 N of force moving the chair 2 m increasing the angle to 20° decreasing the angle to 10° and more.

Power. a measure of the amount of work that can be done in an given amount of time. Watt. the SI unit for power. One watt equals 1 joule of work per second. What are the two things that must happen for work to be done. For work to be done, the force must be applied in the same direction that the object moves.

Lesson 1 - Basic Terminology and Concepts. Definition and Mathematics of Work. Calculating the Amount of Work Done by Forces. Potential Energy. Kinetic Energy. Mechanical Energy. Power. Lesson 2 - The Work-Energy Relationship. Internal vs. External Forces.

potential energy. stored energy. kinetic energy. energy being moved in motion. power equation. power = work/time. work equation. work = force x distance. when a force moves an object through a distance, energy is transferred and work is done on the object.

Work, Energy and Power are fundamental concepts of Physics. Work is said to be done when a force (push or pull) applied to an object causes a displacement of the object. We define the capacity to do the work as energy. Power is the work done per unit of time. This article discusses work, energy and power in detail.

This interactive model explores the relationship between kinetic, potential, and total energy. Students drag markers to create a 1-D curved track, then drag the motion marker to set an initial position. The "hills" can be large or small in height. Click Play and watch the object travel along the user-created curve.

7.1: Work- The Scientific Definition. Work is the transfer of energy by a force acting on an object as it is displaced. The work W that a force F does on an object is the product of the magnitude F of the force, times the magnitude d of the displacement, times the cosine of the angle θ between them. In symbols, W = Fd cos θ. (7.1) The SI unit ...

Introduction to work and energy. Work and energy (part 2) Conservation of energy. What are energy and work? What is kinetic energy? What is gravitational potential energy? What is conservation of energy? Work and the work-energy principle. Work as the transfer of energy.

Honors Assignment - Energy, Work, and Power Reading Chapter 6 Homework Assignment 1: # 1 - 6 Assignment 2: # 8 - 16 Assignment 3: # 17 - 23 Assignment 4: # 24 - 31 Assignment 5: # 32, 33 In Class: # 34 - 36, 38 - 40 Objectives/HW The student will be able to: HW: 1 Define and apply the concepts of kinetic and potential energy and use ...

This video introduces the concepts of work and power. Click Create Assignment to assign this modality to your LMS. We have a new and improved read on this topic. Click here to view We have moved all content for this concept to for better organization. Please update your bookmarks accordingly.

forces such as friction that cause energy to transfer from an object and be dissipated into the surroundings. horsepower. a common unit of power, equal to about 746 watts. power. the rate at which work is done. watt. the metric unit of power. Study with Quizlet and memorize flashcards containing terms like fossil fuels, wood, bonds and more.

How much time is needed to produce 720 Joules of work if 90 watts of power is used? 12. If 68 W of power is produced in 18 seconds, how much work is done? 13. A set of pulleys lifts an 800 N crate 4 meters in 7 seconds. What power was used? Title: Worksheet - Work and Power Problems

Explanation: . Since this question refers to work done by nonconservative forces, we know that: Here, is the change in potential energy, and is a change in kinetic energy. is because the object returns to the same height as when it was launched. however has changed because the object's velocity has changed. Recall that the formula for the change in kinetic energy is given by:

The definition of work, W , is below: W = F ⋅ Δ x. The work we need to do to burn the energy in the candy bar is E = 280 cal ⋅ 4184 J / cal = 1.17 MJ . Therefore, the distance, Δ x , we need to move the box through is: W = F ⋅ Δ x 1.17 MJ = ( 500 N) ⋅ Δ x 1.17 × 10 6 J 500 N = Δ x 2, 340 m = Δ x. Remember, however, that our ...

Work, Energy & Power Quiz. This online quiz is intended to give you extra practice in performing a variety of calculations involving work, energy and power, including kinetic and potential energy. This quiz aligns with the following NGSS standard (s): HS-PS3-1, HS-PS3-2. Select your preferences below and click 'Start' to give it a try! Number ...

Power is the rate at which work is done. When calculating power, you should use the formula P = work divided by time. In this formula, "P" stands for power, W stands for work, and t for time. The SI unit for Power is the Watt. C. Power Problems. W = 100 J P = W/t 5. W = 225 J t = W/P 6.

Work formula. Force x Distance. When can there be no work? Work is done in a circle/no distance is gained or lost. formula for kinetic energy. =1/2mv^2. Formula for power. Work/time. Study with Quizlet and memorize flashcards containing terms like Work, kinetic energy, Potential Energy and more.

Some documents on Studocu are Premium. Upgrade to Premium to unlock it. Work and energy - assignment. University: Nova Southeastern University. Course:Physics I/Lab (PHYS 2400) 91Documents. Students shared 91 documents in this course. Info More info. Download.

Power, Work, and Time • When power and time are known, can be found. • Equation: 𝑃=𝑊/𝑡 • Rearrange to find work:𝑊=𝑃𝑡 When power and work and distance are known, can be found. • Equation: 𝑃=𝑊/𝑡 • Rearrange to find time: 𝑡=𝑊/𝑃 Example: Maria did 3,600 J of work and used 6.0 W of power while moving ...

The Work and Energy module consists of 10 missions (assignments) that address such topics as work, power, kinetic and potential energy, and the relationship between the mechanical energy of an object and the work done upon or by it. The 10 missions and the corresponding objectives are listed below. Tap a mission's name to begin.

0 likes, 0 comments - myassignmenthelpgroup on April 30, 2024: "Let us realize that the privilege to work is a gift, the power to work is a blessing, and the love of ...

6. Two identical twins, Flip and Skip, climb a flight of stairs. Flip climbs the. flight in 30 seconds, while Skip climbs the flight of stairs in 20 seconds. ii. Which twin produces the greatest climbing power? Skip since he produces the same amount. of work against gravity in a smaller interval of tim. Why does the force of gravity do no work ...

The purpose of this RFQ is to initiate a competitive bid process to select a highly qualified On-Call DCBO Firm to assist the STEP Division with compliance oversight for approved project modifications or emergency power plant facility changes for a contract cycle of three years. With the DCBO's assistance, the Compliance Office can ensure that these modifications are completed on schedule ...

92 terms. bkakpo. Preview. Study with Quizlet and memorize flashcards containing terms like What is the transfer of energy to an object using a force that causes the object to move in the direction of the force?, Which of the following is considered work?, One way you can tell that the bowler has done work is that when the ball is moving, it ...