Chapter 5 Work and Energy

Size: px
Start display at page:

Download "Chapter 5 Work and Energy"

Transcription

1 Chapter 5 Work and Energy

2 5.1 Work Done by a Constant Force Definition of work: The work done by a constant force acting on an object is equal to the product of the magnitudes of the displacement and the component of the force parallel to that displacement.

3 5.1 Work Done by a Constant Force In (a), there is a force but no displacement: no work is done. In (b), the force is parallel to the displacement.

4 5.1 Work Done by a Constant Force W = F cos(θ) d Unit of work: newton meter (N m) 1 N m is called 1 joule.

5 5.1 Work Done by a Constant Force What if the force that is applied is in the opposite direction of the displacement? What is the best example of such a force?

6 5.1 Work Done by a Constant Force Friction is a force which always opposes the direction of motion, therefore its work done will always be negative. In the case of lifting an object, gravity works against the motion and therefore does negative work.

7 5.2 Work Done by a Variable Force The force exerted by a spring varies linearly with the displacement:

8 5.2 Work Done by a Variable Force A plot of force versus displacement allows us to calculate the work done:

9 Work Done by a Variable Force F s = -kx (ideal spring force) W = ½kx 2 (work done stretching or compressing a spring)

10 What is ENERGY?!

11 5.3 The Work Energy Theorem: Kinetic Energy Kinetic energy is defined: The net work on an object changes its kinetic energy.

12 5.3 The Work Energy Theorem: Kinetic Energy This relationship is called the work energy theorem.

13 Kinetic Energy

14 5.4 Potential Energy Gravitational potential energy: U = m x g x y

15 5.4 Potential Energy Only changes in potential energy are physically significant; therefore, the point where U = 0 may be chosen for convenience.

16 5.4 Potential Energy Potential energy may be thought of as stored work, such as in a compressed spring or an object at some height above the ground. Work done also changes the potential energy (U) of an object.

17 5.4 Potential Energy We can, therefore, define the potential energy of a spring; note that, as the displacement is squared, this expression is applicable for both compressed and stretched springs.

18 Where does the Energy Go? In a perfect system: When you lose potential energy, you gain kinetic energy Example: Object falls what happens? It speeds up! (increased v increased KE) It loses height (decreased y decreased U) When you gain potential energy it is because you are losing kinetic energy Example: Throw an object upwards what happens? It slows down! (decreased v decreased KE) It gains height! (increased y increased U)

19 Conservation (briefly) This balance between kinetic and potential energy is considered conservative because the total energy does not ever change. E Total = KE + U ΔKE + ΔU = 0 When U goes down, KE goes up When KE goes down, U goes up So by extension: ΔU = -ΔKE True story.

20 Conservation (briefly) And in a not-perfect system? Heat Friction Air Resistance Sound Light But we can just forget that stuff right???

21 Energy Equation Recap Work/Energy W = ΔE W = ΔKE W = ΔU Kinetic Energy (KE) KE = ½ mv 2 Potential Energy (U) Gravitational U = mgy ΔU = mgδy Spring U = ½ kx 2 Total Energy (E) E = KE + U ΔKE + ΔU = 0

22 5.5 Conservation of Energy We observe that, once all forms of energy are accounted for, the total energy of an isolated system does not change. This is the law of conservation of energy: The total energy of an isolated system is always conserved. We define a conservative force: A force is said to be conservative if the work done by it in moving an object is independent of the object s path.

23 5.5 Conservation of Energy So, what types of forces are conservative? Gravity is one; the work done by gravity depends only on the difference between the initial and final height, and not on the path between them. Similarly, a nonconservative force: A force is said to be nonconservative if the work done by it in moving an object does depend on the object s path. The quintessential nonconservative force is friction.

24 5.5 Conservation of Energy Another way of describing a conservative force: A force is conservative if the work done by it in moving an object through a round trip is zero. We define the total mechanical energy:

25 5.5 Conservation of Energy For a conservative force: Many kinematics problems are much easier to solve using energy conservation.

26 5.5 Conservation of Energy All three of these balls have the same initial kinetic energy; as the change in potential energy is also the same for all three, their speeds just before they hit the bottom are the same as well.

27 5.5 Conservation of Energy In a conservative system, the total mechanical energy does not change, but the split between kinetic and potential energy does.

28 5.5 Conservation of Energy If a nonconservative force or forces are present, the work done by the net nonconservative force is equal to the change in the total mechanical energy.

29 What is Power?

30 5.6 Power The average power is the total amount of work done divided by the time taken to do the work. If the force is constant and parallel to the displacement,

31 What is the unit for power?

32 5.6 Power The unit for power, J/s, is more commonly referred to as a Watt (W), named for James Watt whose studies in work, energy, and power helped pave the way for modern machine engines. The British unit, horsepower (hp) is a larger unit still commonly used today: 1 hp = 550 ft lb/s = 746 W

33

34 Practice! 1. Fred pushes boulders for a living. If he applied 450 N of force, moving the boulder 4.0 meters in three minutes How much work has he accomplished? What is Fred s power output 2. Bob the horse outputs 3.73x10 3 J of energy over a 5.00 s period. What is his power output in Watts, what is it in HP?

35 5.6 Power Mechanical efficiency: The efficiency of any real system is always less than 100%.

36 5.6 Power

37 5.6 Equation Recap 1 hp = 746 W

38 Practice! A roller coaster lift system is able to lift a 1600 kg rollercoaster up a height of 34.0 m height in 18.0 seconds What is the power output of this motor? If it took 1.78x10 6 J of energy to accomplish this task, what is the efficiency of the lift system?

Chapter 7 WORK, ENERGY, AND Power Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable Force Power

Chapter 7 WORK, ENERGY, AND Power Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable Force Power Chapter 7 WORK, ENERGY, AND Power Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable Force Power Examples of work. (a) The work done by the force F on this

More information

PHYS-2010: General Physics I Course Lecture Notes Section VI

PHYS-2010: General Physics I Course Lecture Notes Section VI PHYS-2010: General Physics I Course Lecture Notes Section VI Dr. Donald G. Luttermoser East Tennessee State University Edition 2.5 Abstract These class notes are designed for use of the instructor and

More information

Chapter 7 Work and Kinetic Energy

Chapter 7 Work and Kinetic Energy Chapter 7 Work and Kinetic Energy 7-1 Work Done by a Constant Force The definition of work, when the force is parallel to the displacement: SI unit: newton-meter (N m) = joule, J (7-1) 7-1 Work Done by

More information

Chapter 6 Lecture Notes. F = -kx U E = (1/2)kx 2

Chapter 6 Lecture Notes. F = -kx U E = (1/2)kx 2 Chapter 6 Lecture Notes Physics 2414 - Strauss Formulas: W = F d = Fd cosθ K (1/2)mv 2 W net = W NC + W C = K W G = - U G U G = mgh F = -kx U E = (1/2)kx 2 W NC = K + U E = K + U = (1/2)mv 2 + U E f =

More information

Conservation of Energy and Energy Diagrams. Monday, October 24, 11

Conservation of Energy and Energy Diagrams. Monday, October 24, 11 Conservation of Energy and Energy Diagrams Summary Summary Summary Summary Summary The stretch of a spring and the force that caused it The force applied to an ideal spring will be proportional to its

More information

PHYS Look over: Chapter 7 Sections 1-9 Examples 1, 2, 3, 4, 5, 6, 7, 8, Chapter 8 Sections 1-5, 7, 8 Examples 1, 2, 3, 4, 5, 6, 7, 8 PHYS 1111

PHYS Look over: Chapter 7 Sections 1-9 Examples 1, 2, 3, 4, 5, 6, 7, 8, Chapter 8 Sections 1-5, 7, 8 Examples 1, 2, 3, 4, 5, 6, 7, 8 PHYS 1111 PHYS 2211 Look over: Chapter 7 Sections 1-9 Examples 1, 2, 3, 4, 5, 6, 7, 8, Chapter 8 Sections 1-5, 7, 8 Examples 1, 2, 3, 4, 5, 6, 7, 8 PHYS 1111 Look over Chapter 7 Sections 1-8 Examples 2, 3, 4, 5,

More information

Chapter 6 Work and Energy

Chapter 6 Work and Energy Chapter 6 WORK AND ENERGY PREVIEW Work is the scalar product of the force acting on an object and the displacement through which it acts. When work is done on or by a system, the energy of that system

More information

WORK DONE BY A CONSTANT FORCE

WORK DONE BY A CONSTANT FORCE WORK DONE BY A CONSTANT FORCE The definition of work, W, when a constant force (F) is in the direction of displacement (d) is W = Fd SI unit is the Newton-meter (Nm) = Joule, J If you exert a force of

More information

Work and Kinetic Energy

Work and Kinetic Energy Chapter 6 Work and Kinetic Energy PowerPoint Lectures for University Physics, Twelfth Edition Hugh D. Young and Roger A. Freedman Lectures by James Pazun Modified by P. Lam 5_23_2012 Goals for Chapter

More information

Chapter 7: Kinetic Energy and Work

Chapter 7: Kinetic Energy and Work Chapter 7: Kinetic Energy and Work In this chapter, we will study the important concepts of kinetic energy and the closely related concept of work and power. A- Kinetic Energy Kinetic energy is a physical

More information

Energy. Chapter 5. Human history becomes more and more a race between education and catastrophe. H. G. Wells

Energy. Chapter 5. Human history becomes more and more a race between education and catastrophe. H. G. Wells Energy Chapter 5 Human history becomes more and more a race between education and catastrophe. H. G. Wells Forms of Energy Mechanical Chemical Electromagnetic Nuclear Thermal Elastic Sound Energy Weapons

More information

Objectives for Chapter 10 Energy, Work and Simple Machines

Objectives for Chapter 10 Energy, Work and Simple Machines Objectives for Chapter 10 Energy, Work and Simple Machines Student Targets 403. I can identify kinetic energy as a function of velocity. 2. An object that has kinetic energy must be a. moving b. falling

More information

Chapter 7: Work and Energy

Chapter 7: Work and Energy Chapter 7 Lecture Chapter 7: Work and Energy Goals for Chapter 7 Overview energy. Study work as defined in physics. Relate work to kinetic energy. Consider work done by a variable force. Study potential

More information

Chapter 4 Work, energy, and power

Chapter 4 Work, energy, and power Outline Chapter 4 Work, energy, and power 4. Potential energy & Kinetic energy 4.3 Power By Liew Sau Poh 1 Objectives: (a) define the work done by a force dw = F ds (b) calculate the work done using a

More information

Ch 5 Work and Energy. Conceptual Question: 5, 6, 9, 14, 18 Problems:1, 2, 3, 8, 9, 10, 13, 15, 21, 23, 30, 32, 41, 42, 69, 77

Ch 5 Work and Energy. Conceptual Question: 5, 6, 9, 14, 18 Problems:1, 2, 3, 8, 9, 10, 13, 15, 21, 23, 30, 32, 41, 42, 69, 77 Ch 5 Work and Energy Conceptual Question: 5, 6, 9, 14, 18 Problems:1, 2, 3, 8, 9, 10, 13, 15, 21, 23, 30, 32, 41, 42, 69, 77 Work and Energy Work done on an object by a force is: W = F x SI units Joule

More information

Chapter 8 Potential Energy and Conservation of Energy. Copyright 2010 Pearson Education, Inc.

Chapter 8 Potential Energy and Conservation of Energy. Copyright 2010 Pearson Education, Inc. Chapter 8 Potential Energy and Conservation of Energy 8-1 Conservative and Nonconservative Forces Conservative force: the work it does is stored in the form of energy that can be released at a later time

More information

Work, Energy & Power

Work, Energy & Power ork, Energy & Power Classification of Energy Energy Mechanical Energy Non-mechanical Energy Kinetic Energy (Mechanical) Potential Energy Gravitational Elastic Non-Mechanical Energy Nuclear energy Chemical

More information

and 1470 J = mgh out (because GPE = mgh)

and 1470 J = mgh out (because GPE = mgh) The Law of Conservation of Energy states simply that the energy of a system is a constant, even if energy is transformed from one from to another within the system. In other words, the energy put into

More information

7-2 Kinetic Energy and the Work-Energy Theorem

7-2 Kinetic Energy and the Work-Energy Theorem 7-2 Kinetic Energy and the Work-Energy Theorem When positive work is done on an object, its speed increases; when negative work is done, its speed decreases. Copyright 2010 Pearson Education, Inc. 7-2

More information

WEEK 10: WORK AND ENERGY

WEEK 10: WORK AND ENERGY Name Date Partners OBJECTIVES WEEK 10: WORK AND ENERGY To extend the intuitive notion of work as physical effort to a formal mathematical definition of work, W, as a function of both the force on an object

More information

Chapter 10: Energy and Work. Slide 10-2

Chapter 10: Energy and Work. Slide 10-2 Chapter 10: Energy and Work Slide 10-2 Forms of Energy Mechanical Energy K U g U s Thermal Energy Other forms include E th E chem E nuclear The Basic Energy Model An exchange of energy between the system

More information

Physics 2A Chapter 6: Work and Energy. Problem Solving

Physics 2A Chapter 6: Work and Energy. Problem Solving Physics 2A Chapter 6: Work and Energy It is good to have an end to journey toward; but it is the journey that matters, in the end. Ursula K. Le Guin Nobody made a greater mistake than he who did nothing

More information

PHY1 Review for Exam 6. Equations V = 2πr / T a c = V 2 /r. W = Fdcosθ PE = mgh KE = ½ mv 2 E = PE + KE

PHY1 Review for Exam 6. Equations V = 2πr / T a c = V 2 /r. W = Fdcosθ PE = mgh KE = ½ mv 2 E = PE + KE Topics 1. Work 2. Energy a. Potential energy b. Kinetic energy c. Conservation of energy 3. Power Constants g = 9.8 m/s 2 Equations V = 2πr / T a c = V 2 /r F = ma F F = µf N W = Fdcosθ PE = mgh KE = ½

More information

Lecture PowerPoints. Chapter 8 Physics for Scientists and Engineers, with Modern Physics, 4 th edition Giancoli

Lecture PowerPoints. Chapter 8 Physics for Scientists and Engineers, with Modern Physics, 4 th edition Giancoli Lecture PowerPoints Chapter 8 Physics for Scientists and Engineers, with Modern Physics, 4 th edition Giancoli 2009 Pearson Education, Inc. This work is protected by United States copyright laws and is

More information

Work and Energy. Phys 2211L. Introduction

Work and Energy. Phys 2211L. Introduction Work and Energy Phys 2211L Introduction In this lab you will use the Work-Energy Theorem to predict the motion of a object in three different cases. You will work with your lab partner(s) to develop a

More information

Name: Partners: Period: Coaster Option: 1. In the space below, make a sketch of your roller coaster.

Name: Partners: Period: Coaster Option: 1. In the space below, make a sketch of your roller coaster. 1. In the space below, make a sketch of your roller coaster. 2. On your sketch, label different areas of acceleration. Put a next to an area of negative acceleration, a + next to an area of positive acceleration,

More information

Advanced Placement. PHYSICS B Work, Energy, & Power

Advanced Placement. PHYSICS B Work, Energy, & Power Advanced Placement PHYSICS B Work, Energy, & Power Student 2013-2014 Work, Energy, & Power What I Absolutely Have to Know to Survive the AP* Exam Work is the defined quantity from which the entire theory

More information

Physics 201 Homework 5

Physics 201 Homework 5 Physics 201 Homework 5 Feb 6, 2013 1. The (non-conservative) force propelling a 1500-kilogram car up a mountain -1.21 10 6 joules road does 4.70 10 6 joules of work on the car. The car starts from rest

More information

Phys101 Lectures 8 and 9 Conservation of Mechanical Energy

Phys101 Lectures 8 and 9 Conservation of Mechanical Energy Phys101 Lectures 8 and 9 Conservation of Mechanical Energy Key points: Conservative and Nonconservative Forces Potential Energy Generalized work-energy principle Mechanical Energy and Its Conservation

More information

I was NOT able to find the following students in webassign: Meredith Pean Courtney Schwing Renan Vappie

I was NOT able to find the following students in webassign: Meredith Pean Courtney Schwing Renan Vappie I was NOT able to find the following students in webassign: Meredith Pean Courtney Schwing Renan Vappie If you are still in this section, please login in webassign now. Power Forces Conservative Force:

More information

PHYSICS 149: Lecture 15

PHYSICS 149: Lecture 15 PHYSICS 149: Lecture 15 Chapter 6: Conservation of Energy 6.3 Kinetic Energy 6.4 Gravitational Potential Energy Lecture 15 Purdue University, Physics 149 1 ILQ 1 Mimas orbits Saturn at a distance D. Enceladus

More information

AP1 WEP. Answer: E. The final velocities of the balls are given by v = 2gh.

AP1 WEP. Answer: E. The final velocities of the balls are given by v = 2gh. 1. Bowling Ball A is dropped from a point halfway up a cliff. A second identical bowling ball, B, is dropped simultaneously from the top of the cliff. Comparing the bowling balls at the instant they reach

More information

Chapter 7 Work and Kinetic Energy

Chapter 7 Work and Kinetic Energy Chapter 7 Work and Kinetic Energy Which one costs energy? Question: (try it) How to throw a baseball to give it large speed? Answer: Apply large force across a large distance! Force exerted through a distance

More information

WORK - ENERGY. Work i = F net s cos(θ) (1.2)

WORK - ENERGY. Work i = F net s cos(θ) (1.2) 1 Object WORK - ENERGY To investigate the work-kinetic energy relationship and conservation of energy. Apparatus Track and associated stops, one dynamics cart, one photogate timer, interface equipment,

More information

Springs. Spring can be used to apply forces. Springs can store energy. These can be done by either compression, stretching, or torsion.

Springs. Spring can be used to apply forces. Springs can store energy. These can be done by either compression, stretching, or torsion. Work-Energy Part 2 Springs Spring can be used to apply forces Springs can store energy These can be done by either compression, stretching, or torsion. Springs Ideal, or linear springs follow a rule called:

More information

Conservation of Energy 1 of 9

Conservation of Energy 1 of 9 Conservation of Energy 1 of 9 Conservation of Energy The important conclusions of this chapter are: If a system is isolated and there is no kinetic friction (no non-conservative forces), then KE + PE =

More information

PRE-LAB FOR CONSERVATION OF ENERGY

PRE-LAB FOR CONSERVATION OF ENERGY Name: Conservation of Energy, p. 1/13 PRE-LAB FOR CONSERVATION OF ENERGY Directions: Read over the lab and answer the following questions. 1. How is gravitational potential energy defined in this lab?.

More information

CHAPTER 6 WORK AND ENERGY

CHAPTER 6 WORK AND ENERGY CHAPTER 6 WORK AND ENERGY CONCEPTUAL QUESTIONS. REASONING AND SOLUTION The work done by F in moving the box through a displacement s is W = ( F cos 0 ) s= Fs. The work done by F is W = ( F cos θ). s From

More information

Chapter 8: Conservation of Energy

Chapter 8: Conservation of Energy Chapter 8: Conservation of Energy This chapter actually completes the argument established in the previous chapter and outlines the standing concepts of energy and conservative rules of total energy. I

More information

Chapter F. Work and Energy. Blinn College - Physics Terry Honan

Chapter F. Work and Energy. Blinn College - Physics Terry Honan Chapter F Work and Energy Blinn College - Physics 2425 - Terry Honan F. - Introduction to Work Mechanical Advantage In Chapter D we considered the example of a pulley system lifting a weight. We saw that

More information

If a force is applied to an object, the object may experience a change in position, i.e., a displacement.

If a force is applied to an object, the object may experience a change in position, i.e., a displacement. If a force is applied to an object, the object may experience a change in position, i.e., a displacement. CHAPTER 6 When a net force is applied over a distance, say, to move an object, mechanical work

More information

Chapter 7. The product of the magnitude of the gravitational force (mg) and the height (y) above the ground is called the gravitational potential

Chapter 7. The product of the magnitude of the gravitational force (mg) and the height (y) above the ground is called the gravitational potential Chapter 7 Potential Energy An object that has kinetic energy can do work on some other object. However, work can be done on a system without increasing the system s total kinetic energy. In this case,

More information

9 Energy. Energy can change from one. loss or gain.

9 Energy. Energy can change from one. loss or gain. Energy can change from one form to another without a net loss or gain. 9.1 Work Main Idea: Work is done when a net force acts on an object and the object moves in the direction of the net force. 9.1 Work

More information

Ch 8 Potential energy and Conservation of Energy. Question: 2, 3, 8, 9 Problems: 3, 9, 15, 21, 24, 25, 31, 32, 35, 41, 43, 47, 49, 53, 55, 63

Ch 8 Potential energy and Conservation of Energy. Question: 2, 3, 8, 9 Problems: 3, 9, 15, 21, 24, 25, 31, 32, 35, 41, 43, 47, 49, 53, 55, 63 Ch 8 Potential energ and Conservation of Energ Question: 2, 3, 8, 9 Problems: 3, 9, 15, 21, 24, 25, 31, 32, 35, 41, 43, 47, 49, 53, 55, 63 Potential energ Kinetic energ energ due to motion Potential energ

More information

= KE + U. Only conservative forces (gravity & spring) cause energy transfer (work)

= KE + U. Only conservative forces (gravity & spring) cause energy transfer (work) Mechanical energy: h = KE + U Only conservative forces (gravity & spring) cause energy transfer (work) W net = ΔKE Sec. 7-3 W conservative = ΔU Sec. 8-1 Isolated system: Assuming only internal forces (no

More information

PHYS 1020 Lecture 18 Work Energy

PHYS 1020 Lecture 18 Work Energy PHYS 1020 Lecture 18 Work Energy Work done by a constant force Since -1 cosθ 1, W can be positive or negative. See lecture posted online for corrected version. You can calculate the work done on an object

More information

Practice Problems with Solutions - Based Chapter 8 and 9, and good review for Midterm 1. Physics 11a Fall 2010

Practice Problems with Solutions - Based Chapter 8 and 9, and good review for Midterm 1. Physics 11a Fall 2010 Practice Problems with Solutions - Based Chapter 8 and 9, and good review for Midterm 1. Physics 11a Fall 2010 1. You push on a crate, and it starts to move but you don t. Draw a free-body diagram for

More information

Work and Energy. This is Fundamental to Engineering. Definition of Work. W=F. d

Work and Energy. This is Fundamental to Engineering. Definition of Work. W=F. d Work and Energy This is Fundamental to Engineering Definition of Work W=F. d Work done and Work experienced Something subtle: The amount of work YOU do on a body may not be the same as the work done ON

More information

Lecture 16 Energy. Conservation of Energy (including W nc and W ext ) Elastic vs. Inelastic Collisions

Lecture 16 Energy. Conservation of Energy (including W nc and W ext ) Elastic vs. Inelastic Collisions Lecture 16 Energy Conservation of Energy (including W nc and W ext ) Elastic vs. Inelastic Collisions Another issue we haven t dealt with yet is what to do when a force like friction does work. Work is

More information

7. Kinetic Energy and Work

7. Kinetic Energy and Work Kinetic Energy: 7. Kinetic Energy and Work The kinetic energy of a moving object: k = 1 2 mv 2 Kinetic energy is proportional to the square of the velocity. If the velocity of an object doubles, the kinetic

More information

C h a p t e r 1 4 Work, Power and Simple Machines

C h a p t e r 1 4 Work, Power and Simple Machines C h a p t e r 1 4 Work, Power and Simple Machines Questions to think about before What does work mean to you??? List some examples of work: Is this work??? Work & Science Now...think about work in terms

More information

WORK - ENERGY. Work i = F net s cos(θ) (1.2)

WORK - ENERGY. Work i = F net s cos(θ) (1.2) 1 Object WORK - ENERGY To investigate the work-kinetic energy relationship and conservation of energy. Apparatus Track and associated stops, one dynamics cart, PVC tube, one photogate timer, one force

More information

Section 4: Conservation of (Mechanical) Energy

Section 4: Conservation of (Mechanical) Energy Section 4: Conservation of (Mechanical) Energy Student Objectives: Determine the total energy of an object by finding both the kinetic and potential energies of that object. Recognize that when no external

More information

8. Potential Energy and Conservation of Energy Potential Energy: When an object has potential to have work done on it, it is said to have potential

8. Potential Energy and Conservation of Energy Potential Energy: When an object has potential to have work done on it, it is said to have potential 8. Potential Energy and Conservation of Energy Potential Energy: When an object has potential to have work done on it, it is said to have potential energy, e.g. a ball in your hand has more potential energy

More information

Work. Work = Force distance (the force must be parallel to movement) OR Work = (Force)(cos θ)(distance)

Work. Work = Force distance (the force must be parallel to movement) OR Work = (Force)(cos θ)(distance) Work Work = Force distance (the force must be parallel to movement) OR Work = (Force)(cos θ)(distance) When you are determining the force parallel to the movement you can do this manually and keep track

More information

Potential Energy and Energy Conservation

Potential Energy and Energy Conservation Chapter 7 Potential Energy and Energy Conservation PowerPoint Lectures for University Physics, Thirteenth Edition Hugh D. Young and Roger A. Freedman Lectures by Wayne Anderson Goals for Chapter 7 To use

More information

Physics 107 HOMEWORK ASSIGNMENT #6

Physics 107 HOMEWORK ASSIGNMENT #6 Physics 107 HOMEWORK ASSIGNMENT #6 Cutnell & Johnson, 7 th edition Chapter 6: Problems 10, 4, 30, 4, 6 *10 A 55-kg box is being pushed a distance of 7.0 m across the floor by a force whose magnitude is

More information

THE WORK OF A FORCE, PRINCIPLE OF WORK AND ENERGY, & PRINCIPLE OF WORK AND ENERGY FOR A SYSTEM OF PARTICLES

THE WORK OF A FORCE, PRINCIPLE OF WORK AND ENERGY, & PRINCIPLE OF WORK AND ENERGY FOR A SYSTEM OF PARTICLES THE WORK OF A FORCE, PRINCIPLE OF WORK AND ENERGY, & PRINCIPLE OF WORK AND ENERGY FOR A SYSTEM OF PARTICLES Today s Objectives: Students will be able to: 1. Calculate the work of a force. 2. Apply the

More information

WORK AND ENERGY. Work done by a constant force. Gravitational Potential Energy

WORK AND ENERGY. Work done by a constant force. Gravitational Potential Energy WORK AND ENERGY Work done by a constant force Kinetic Energy Gravitational Potential Energy Simple Machines The ideas we shown above were developed in the generation after Newton. Here we will discuss

More information

LAB 6: WORK AND ENERGY

LAB 6: WORK AND ENERGY 87 Name Date Partners LAB 6: WORK AND ENERGY OBJECTIVES OVERVIEW Energy is the only life and is from the Body; and Reason is the bound or outward circumference of energy. Energy is eternal delight. William

More information

Chapter 7- Linear Momentum

Chapter 7- Linear Momentum Chapter 7- Linear Momentum Assignment 6 Textbook (Giancoli, 6 th edition), Chapter 6: Due on Thursday, November 12 1. On page 163 of Giancoli, problem 38. 2. On page 165 of Giancoli, problem 69. 3. On

More information

Potential Energy. So far: Considered all forces equal, calculate work done by net force only => Change in kinetic energy. Analogy: Pure Cash Economy

Potential Energy. So far: Considered all forces equal, calculate work done by net force only => Change in kinetic energy. Analogy: Pure Cash Economy Potential Energy So far: Considered all forces equal, calculate work done by net force only => Change in kinetic energy. Analogy: Pure Cash Economy But: Some forces seem to be able to store the work for

More information

W in = GPE out 1470 J = GPE out Why, 1470 J, of course! The energy from Work has to go somewhere

W in = GPE out 1470 J = GPE out Why, 1470 J, of course! The energy from Work has to go somewhere The Law of Conservation of Energy states simply that the energy of a system is a constant, even if energy is transformed from one from to another within the system. In other words, the energy put into

More information

Chapter 6: Conservation of Energy

Chapter 6: Conservation of Energy Chapter 6: Conservation o Energy Introduction Energy ability to perorm work. Unit o energy (and o work) Joules (J) 1 J = 1 kg- m 2 / s 2 Forms o energy: Light, chemical, nuclear, mechanical, electrical,

More information

Section 1 Work, Power, and Machines

Section 1 Work, Power, and Machines CHAPTER OUTLINE Section 1 Work, Power, and Machines Key Idea questions > How is work calculated? > What is the relationship between work and power? > How do machines make work easier? What Is Work? > How

More information

Chapter 8 Potential Energy and Conservation of Energy. Copyright Dr. Weining Man and Pearson

Chapter 8 Potential Energy and Conservation of Energy. Copyright Dr. Weining Man and Pearson Chapter 8 Potential Energy and Conservation of Energy Units of Chapter 8 Conservative and Nonconservative Forces Potential Energy and the Work Done by Conservative Forces Conservation of Mechanical Energy

More information

Work or Not. Work: Example 4. Lab Comments 6/3/2013. Work = Force X distance W = Fd W = Fdcosq

Work or Not. Work: Example 4. Lab Comments 6/3/2013. Work = Force X distance W = Fd W = Fdcosq Work = Force X distance W = Fd W = Fdcosq Unit Joules Force must be direction of motion W NET = DKE Work or Not 1. A teacher pushes against a wall until he is exhausted. 2. A book falls off the table and

More information

Work, Energy and Power

Work, Energy and Power Work, Energy and Power In this section of the Transport unit, we will look at the energy changes that take place when a force acts upon an object. Energy can t be created or destroyed, it can only be changed

More information

2 of 19 10/10/ :21 AM where is the spring constant of the cord and is the extension of the cord Express your answer in terms of the cord's final

2 of 19 10/10/ :21 AM where is the spring constant of the cord and is the extension of the cord Express your answer in terms of the cord's final 1 of 19 10/10/2007 04:21 AM Assignment Display Mode: View Printable Answers Course TUPH1061F07 Homework Ch 7 Due 4 Oct Due at 12:00pm on Wednesday, October 10, 2007 View Grading Details Bungee Jumping

More information

Recap - Forces. Action = - Reaction. Newton s first law:

Recap - Forces. Action = - Reaction. Newton s first law: Newton s first law: Newton s second law: Recap - Forces An object moves with a velocity that is constant in magnitude and direction unless a non-zero net force acts on it. Newton s 3rd law: Action = -

More information

Gravitational Potential Energy

Gravitational Potential Energy Gravitational Potential Energy Consider a ball falling from a height of y 0 =h to the floor at height y=0. A net force of gravity has been acting on the ball as it drops. So the total work done on the

More information

Work and Energy Notes

Work and Energy Notes Work and Energy Notes In this unit our study of motion is going to be approached from the perspective of work and energy. Work In physics, work is defined as a force acting upon an object to cause a displacement.

More information

Lab 8: Work and Energy

Lab 8: Work and Energy Lab 8: Work and Energy Objectives: To understand the concept of work To be able to calculate work for constant and non-constant forces To understand the concept of kinetic energy To understand the relationship

More information

LAB 8: WORK AND ENERGY

LAB 8: WORK AND ENERGY Lab 8 - Work and Energy 89 Name Date Partners LAB 8: WORK AND ENERGY Energy is the only life and is from the Body; and Reason is the bound or outward circumference of energy. Energy is eternal delight.

More information

Chapter 7 Work and Kinetic Energy Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable Force Power

Chapter 7 Work and Kinetic Energy Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable Force Power Chapter 7 Work and Kinetic Energy Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable Force Power 7-1 Work Done by a Constant Force The definition of work,

More information

Work and Energy. Work

Work and Energy. Work Work and Energy The motion of a particle can be examined with the method of work and energy. Although many problems can be solved through Newton's second law, work and energy are very useful tools which

More information

Exam. Name. TRUE/FALSE. Write ʹTʹ if the statement is true and ʹFʹ if the statement is false. 1) Kinetic energy is proportional to speed.

Exam. Name. TRUE/FALSE. Write ʹTʹ if the statement is true and ʹFʹ if the statement is false. 1) Kinetic energy is proportional to speed. Exam Name TRUE/FALSE. Write ʹTʹ if the statement is true and ʹFʹ if the statement is false. 1) Kinetic energy is proportional to speed. 2) The gravitational force is a conservative force. 3) If work is

More information

Energy Approach to Problems. Ch 7: Energy and Energy Transfer. Environment. Systems

Energy Approach to Problems. Ch 7: Energy and Energy Transfer. Environment. Systems Ch 7: Energy and Energy Transfer The concept of energy is one of the most important topics in science Every physical process that occurs in the Universe involves energy and energy transfers or transformations

More information

Energy [J] is defined as the ability to do work. Or Work is the Energy supplied to on object to make it move.

Energy [J] is defined as the ability to do work. Or Work is the Energy supplied to on object to make it move. Work and Energy Work (W) is done on an object by an force when the object moves through a distance (displacement). Since Force and displacement are vectors, work has to be a scalar. We use the scalar product:

More information

Energy and Momentum Test Review Explanations

Energy and Momentum Test Review Explanations 1. Zero net work on an object means that no net energy is being transferred into or out of the object, so the object is not changing its speed. In the given graph, the object's speed is only changing during

More information

a. TRUE - Power is a rate quantity and thus time-based since rate means (something/time)

a. TRUE - Power is a rate quantity and thus time-based since rate means (something/time) 1. Which of the following statements is not true about power? a. Power is a time-based quantity. b. Power refers to how fast work is done upon an object. c. A force is exerted on an object to move it at

More information

Chapter 8. Potential Energy. Potential energy is the energy associated with the configuration of a system of objects that exert forces on each other

Chapter 8. Potential Energy. Potential energy is the energy associated with the configuration of a system of objects that exert forces on each other Chapter 8 Potential Energy Potential Energy Potential energy is the energy associated with the configuration of a system of objects that exert forces on each other This can be used only with conservative

More information

Chapter 7 Kinetic Energy Mechanical Energy Conservation of Mechanical Energy Non-Conservative Forces Simple Machines

Chapter 7 Kinetic Energy Mechanical Energy Conservation of Mechanical Energy Non-Conservative Forces Simple Machines Lecture 8 Chapter 7 Kinetic Energy Mechanical Energy Conservation of Mechanical Energy Non-Conservative Forces Simple Machines Kinetic Energy (KE) Energy associated with motion. Kinetic energy of an object

More information

Physics 2A (Fall 2012) Chapter 10: Energy and Work

Physics 2A (Fall 2012) Chapter 10: Energy and Work Physics 2A (Fall 2012) Chapter 10: Energy and Work It is good to have an end to journey toward; but it is the journey that matters, in the end. Ursula K. Le Guin Nobody made a greater mistake than he who

More information

Ch 7 Kinetic Energy and Work. Question: 7 Problems: 3, 7, 11, 17, 23, 27, 35, 37, 41, 43

Ch 7 Kinetic Energy and Work. Question: 7 Problems: 3, 7, 11, 17, 23, 27, 35, 37, 41, 43 Ch 7 Kinetic Energy and Work Question: 7 Problems: 3, 7, 11, 17, 23, 27, 35, 37, 41, 43 Technical definition of energy a scalar quantity that is associated with that state of one or more objects The state

More information

Chapter 6: Energy and Oscillations. 1. Which of the following is not an energy unit? A. N m B. Joule C. calorie D. watt E.

Chapter 6: Energy and Oscillations. 1. Which of the following is not an energy unit? A. N m B. Joule C. calorie D. watt E. Chapter 6: Energy and Oscillations 1. Which of the following is not an energy unit? A. N m B. Joule C. calorie D. watt E. kwh 2. Work is not being done on an object unless the A. net force on the object

More information

Solutions to Homework Set #7 Phys2414 Fall 2005

Solutions to Homework Set #7 Phys2414 Fall 2005 Solution Set #7 Solutions to Homework Set #7 Phys244 Fall 2005 Note: The numbers in the boxes correspond to those that are generated by WebAssign. The numbers on your individual assignment will vary. Any

More information

Work, Power and Potential energy

Work, Power and Potential energy Lecture 10 Work, Power and Potential energy Pre-reading: KJF 10.1 and 10.2 What is Energy? Energy is needed to do useful work. Energy can move things, heat things up, cool them down, join things, break

More information

Chapter 8: Potential Energy and Conservation of Energy. Work and kinetic energy are energies of motion.

Chapter 8: Potential Energy and Conservation of Energy. Work and kinetic energy are energies of motion. Chapter 8: Potential Energy and Conservation of Energy Work and kinetic energy are energies of motion. Consider a vertical spring oscillating with mass m attached to one end. At the extreme ends of travel

More information

Name: Lab Partner: Section:

Name: Lab Partner: Section: Chapter 6 Energy Name: Lab Partner: Section: 6.1 Purpose In this experiment, energy and work will be explored. The relationship between total energy, kinetic energy and potential energy will be observed.

More information

Kinetic Energy and Energy Conservation

Kinetic Energy and Energy Conservation Kinetic Energy and Energy Conservation Physics 1425 Lecture 13 Michael Fowler, UVa Moving Things Have Energy Energy is the ability to do work: to deliver a force that acts through a distance. Placing a

More information

charge is detonated, causing the smaller glider with mass M, to move off to the right at 5 m/s. What is the

charge is detonated, causing the smaller glider with mass M, to move off to the right at 5 m/s. What is the This test covers momentum, impulse, conservation of momentum, elastic collisions, inelastic collisions, perfectly inelastic collisions, 2-D collisions, and center-of-mass, with some problems requiring

More information

± PSS 6.1 Work and Kinetic Energy

± PSS 6.1 Work and Kinetic Energy skiladæmi 5 Due: 11:59pm on Wednesday, October 7, 2015 You will receive no credit for items you complete after the assignment is due. Grading Policy ± PSS 6.1 Work and Kinetic Energy Learning Goal: To

More information

This is word that means a lot of things depending on the context:

This is word that means a lot of things depending on the context: Work and Energy Energy This is word that means a lot of things depending on the context: 1. Energy Consumption of a Household 2. Energy Drinks 3. Auras & Spiritual Energy 4. Renewable Energy Energy as

More information

General Physics I. Lecture 4: Work and Kinetic Energy. Prof. WAN, Xin ( 万歆 )

General Physics I. Lecture 4: Work and Kinetic Energy. Prof. WAN, Xin ( 万歆 ) General Physics I Lecture 4: Work and Kinetic Energy Prof. WAN, Xin ( 万歆 ) xinwan@zju.edu.cn http://zimp.zju.edu.cn/~xinwan/ What Have We Learned? Motion of a particle in any dimensions. For constant acceleration,

More information

Work & kinetic energy

Work & kinetic energy Work & kinetic energy Announcements: CAPA homework #5 due Tues at 10pm MC Exam scores are available on D2L Will not be available during reg. office hours 1-2pm today, but I am available between 2-4pm Beginning

More information

Work Done by Friction. Review. Conservation of Energy. Power

Work Done by Friction. Review. Conservation of Energy. Power Work one by riction riction is a prime example of a non-conservative force. Let s consider moving a book along a table. Looking down at the tabletop. B Review Conservation of Energy 1 µn µn 2 Power A µn

More information

Potential Energy and Conservation of Energy

Potential Energy and Conservation of Energy Last Chapter: Kinetic energy and work Chapter 8 Potential Energy and Conservation of Energy 8-1 Potential Energy Five sections S-1: Potential Energy S-2: Conservation of Mechanical Energy: S-3: Reading

More information

At the skate park on the ramp

At the skate park on the ramp At the skate park on the ramp 1 On the ramp When a cart rolls down a ramp, it begins at rest, but starts moving downward upon release covers more distance each second When a cart rolls up a ramp, it rises

More information

A 1,800 B 5,000 C 100,000 D

A 1,800 B 5,000 C 100,000 D Slide 1 / 35 1 driver in a 2000 kg Porsche wishes to pass a slow moving school bus on a 4 lane road. What is the average power in watts required to accelerate the sports car from 30 m/s to 60 m/s in 9

More information