Presentation on theme: "Work and Energy Chapter 4"— Presentation transcript:
1Work and Energy Chapter 4 Motion and ForcesWork and EnergyChapter 4
2Bell Work 2/22/11Write each statement, then decide if the statement is true or false, if false correct it.An object has acceleration if its velocity is changing.Force is measured in joules.Gravity is a force.
3How do you work?Do you think you did more work the first time you lifted the book or the second time you lifted the book?What do you think work means?
4Work is the use of force to move an object. Work is done by a force that acts in the same direction as the motion of an object.Work = Force • distancepart of forcedoing workpart of force not doing workobjectapplied forcedirection of motionapplied forceobjectdirection of motion
513.1 Work is the use of force to move an object. SIMUALATION Determine how much work is done by lifting weights of different masses.
64.1 Vocab Work - The use of force to move an object over a distance. Joule - The unit used to measure work; one joule of work is done when a force of one newton moves an object one meter.
7Bell Work 2/23/11What two factors do you need to know to calculate how much work was done in any situation?If you push very hard on an object but it does not move, have you done work? Explain,Tina lifted a box 3 m. She used a force of 25 N. How much work did Tina do on the box? Show your work!
8Bell Work 2/22/10If you apply a force of one Newton to a box as you push it for one meter. How many joules of work have you done?If you push a cart with a force of 50 N for 3 m, how much work will you do?Give an example of work that you have done. Name the object that was moved and the distance over which it moved.
9Vocab 4.2Potential energy - Stored energy, or the energy an object has due to its position.Calculating potential energyGravitational Potential Energy = mass x gravitational acceleration x heightGPE = mgh (on earth g = 9.8 m/s2)
10MGH Example 1: What is the gravitational potential energy of a girl who has a mass of 40 kg and is standing on the edge of a diving board that is 5 m above the water?
11MGH Example 2: An apple with a mass of 0 MGH Example 2: An apple with a mass of 0.1 kg is attached to a branch of an apple tree 4 m from the ground. How much gravitational potential energy does the apple have?
12Kinetic Energy - The energy of motion; a moving object has the most kinetic energy at the point where it moves the fastest.Calculating Kinetic EnergyKinetic energy = mass x velocity22KE = 0.5 m (v2)
13KE Example 1: What is the kinetic energy of a girl who has a mass of 40 kg and a velocity of 3 m/s?
14KE Example 2: A truck with a mass of 6000 kg is traveling north on a highway at a speed of 17 m/s. What is the kinetic energy of the truck?
15Mechanical energy - A combination of the kinetic energy and potential energy an object has. Calculating mechanical energyMechanical Energy = Potential Energy + Kinetic EnergyME = PE + KE
16ME Example: How much mechanical energy does a skateboarder have that has a potential energy of 200 joules due to his position at the top of a hill and a kinetic energy of 100 joules due to his motion?
17Conservation of energy - A law stating that no matter how energy is transferred or transformed, all of the energy is still present in one form or another.Top of Ramp100%PE1At the top of the ramp, the skater’s mechanical energy is equal to her potential energy because she has no velocity.
18Halfway Down Ramp 50% KE PE 2 As the skater goes down the ramp, she loses height but gains speed. The potential energy she loses is equal to the kinetic energy she gains.
19Bottom of Ramp100%KE3As the skater speeds along the bottom of the ramp, all of the potential energy has changed to kinetic energy. Her mechanical energy remains unchanged.
20Forms of EnergyThermal energy – the energy an object has due to the motion of its moleculesChemical energy – the energy stored in chemical bonds that hold chemical compounds together.Nuclear energy – the potential energy stored in the nucleus of an atomElectromagnetic energy – the energy associated with electrical and magnetic interactions
21Bell Work 2/24/11What is an Independent Variable? (IV)What is a Dependent Variable? (DV)What is a control?What are constants?
22Bell Work – 3/2/11Yelena holds a 10 kg ball over her head at a height of 25 m. What is the GPE of the ball?Quentin has a mass of 75 kg. When he rides his scooter at a velocity of 15 m/s, what is his kinetic energy?What is the formula for mechanical energy?
23Bell Work 2/24/10 What is the law of conservation of energy? Describe 3 different forms of energy.
24Bell Work 3/3/11A dumbbell weighing 20 kg is stored on a shelf 0.75 m high. How much gravitational potential energy does the dumbbell have?2. How much work is done in lifting a 12 N hammer from the floor to a height of 2 m?3. What is the mass of an apple sitting on top of a 12.5 m shelf that has a GPE of 25J?
25Bell Work 3/4/11Draw the following picture and label where the greatest and least PE and KE would be.
26Science Fair 1. Problem 2. Independent Variable (IV) Find your 2 favorite projects and write down the following information about eachTitle1. Problem2. Independent Variable (IV)3. Dependent Variable (DV)4. Summarize the experiment
27What was your favorite science fair project yesterday? Bell Work 2/26/10What was your favorite science fair project yesterday?Write 3 sentences explaining the project and why it was your favorite project.
28Bell Work 3/7/11Match the correct term to each definition – write the definition and the termTerms – mechanical energy, potential energy, kinetic energy, workStored energyThe use of force to move an object a certain distanceThe energy of motion
29The rate at which work is done. 13.3Power is the rate at which work is done.powerpowerwattThe rate at which work is done.horsepowerCHAPTERRESOURCESKEY CONCEPTSUMMARY
3013.3Power is the rate at which work is done.powerwattwattThe unit used to measure power; one watt is equal to one joule of work done in one second.horsepowerCHAPTERRESOURCESKEY CONCEPTSUMMARY
3113.3Power is the rate at which work is done.powerhorsepowerwattThe unit of measurement for engines and motors; one horsepower equals 745 watts.horsepowerCHAPTERRESOURCESKEY CONCEPTSUMMARY
32Power can be calculated from work and time Power = worktimeThe unit of power is always a Watt (W)
33Calculating power from work Example: An Antarctic explorer uses 6000 J of work to pull his sled for 60 s. What power does he need?
34Calculating power from work Example 2: If a conveyor belt uses 10 J to move a piece of candy a distance of 3 m in 20 s, what is the conveyor belt’s power?
35Calculating power from work Example 3: An elevator uses a force of 1710 N to lift 3 people up 1 floor. Each floor is 4 m high. The elevator takes 4 s to lift the 3 people up 1 floor. What is the elevators power?
36Calculating power from Energy Power = EnergytimeThe unit for power is Watts (W)
37Calculating power from Energy Example 1: A light bulb used 600 J of energy in 6 s. What is the power of the light bulb?
38Calculating power from Energy Example 2: A laptop computer uses 100 J every 2 seconds. How much power is needed to run the computer?
39Calculating power from Energy Example 3: The power needed to pump blood through your body is about 1.1 W. How much energy does your body use when pumping blood for 10 seconds?
40Power is the rate at which work is done. 13.3Power is the rate at which work is done.Power can be calculated from work and time.Power =WorktimepowerwatthorsepowerPower can be calculated from energy and time.Power =EnergytimeCHAPTERRESOURCESPower is measured in watts (W) and sometimeshorsepower (hp).SECTIONOUTLINE
41Bell work 3/8/11 How is power related to work? What do you need to know to calculate how much energy a light bulb uses?Which takes more power: lighting a 50 W bulb, 75 W bulb, or 100 W bulb?
42Chapter Resources Click on the items below to access resources on CHAPTER HOMEChapter ResourcesImage GalleryClick here to review chapterimages and animationsReview GamePlay a fun interactivereview gameAnimationsLink to all the McDougalLittell Science animationsClick on the items below to access resources onCLASSZONE.COMAudio ReadingsHear chapter audio readingsResource CentersGet more information on select sciencetopicsContent ReviewReview key concepts and vocabularyStandardized Test PracticePractice state standardized testsMath TutorialReview math conceptsBACK TO CHAPTER
43Bell Work 3/5/10George is pushing a box across the floor at an angle and the box is moving only forward. Does all of George’s force do work on the box? Explain.
44Bell Work 3/8/10Get out the Power House Web Worksheet from last week and make sure you have the 4 questions on the front answered
45Bell Work 3/9/10 Motion is a change in _______ over time Jenna knows that a friend runs 100m in 8 s. She could use this to calculate her friend’s ________Elena is riding her bicycle. She begins pedaling harder. Her ______ will increase.Speed in a specific direction is ______Acceleration measures a change in _____Latitude and longitude measure _____You need to know ______ and _____ to measure speed
46Article Review Title and author of article Who the article involves Include the following in complete sentencesTitle and author of articleWho the article involvesWhat happened in the articleWhere the article took placeWhen the article was writtenWhy the article is important (2 sent.)How it relates to science (2 sent.)
47Bell Work 3/11/101. Mary has a mass of 60 kg. When she rides her bike at a velocity of 4 m/s, what is his kinetic energy? KE = 1/2mv2.2.The total mechanical energy of an object is 1500 J. If the kinetic energy of the object is 750 J, then the potential energy of the object is (ME = KE + PE)3. Tyler applies a 150 N force for 15 s to slide a box 20 m across the floor. What is Tyler’s power? (P = W/t) (W = Fd)
48Bell Work 3/12/10Identify the action/reaction force pair involved when you catch a ball.Explain the difference between balanced forces and action/reaction forces.A man pushes on a wall with a force of 50 N. What are the size and the direction of the force that the wall exerts on the man?
49What is your favorite type of ride to go on? Bell Work 3/15/10What is your favorite type of ride to go on?What is your favorite roller coaster and why?
50Bell Work 3/16/10What do you think the most difficult part will be when building your roller coaster? Why?What information would you like to find today in order to help you with the building of your roller coaster?
51Bell Work 3/17/10 Happy St. Patrick’s Day! Try this trivia. What colors are in the Ireland flag?What is the capital city of Ireland?How many leaves are on a lucky clover?What did St. Patrick drive out of Ireland? (snakes, a car, Leprechauns)Where do you find a pot of gold?What happens if you look away from a Leprechaun?
52Green, Orange, WhiteThe colors in the flag have meaning: Green is for the North, orange is for the South and white is the Peace that binds them
53Dublin, IrelandDublin, Ireland is the third most visited capital city in Europe.
54Four4. According to the Guiness Book of World Records the most leaves ever found on a clover is 14.
55SnakesAccording to the legend, St. Patrick drove all the snakes in Ireland out of the country and into the sea.
56At the end of a rainbowIf you are looking for a pot of gold go to the end of a rainbow and see if a Leprechaun has hidden one there.
57He DisappearsIf you are lucky enough to find a leprechaun don’t take your eyes off of him, if you do he will disappear with his pot of gold.
58Bell Work 3/18/10 What is the formula for speed? Calculate the speed of a car traveling 300 meters in 20 seconds.Calculate the speed of your marble if it complete the 6 meter track in 12 seconds.
59Bell Work 3/19/10Draw and label the eight phases of the moon. Use the space science book if you need help.