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Physics HS/Science Unit: 05 Lesson: 01 Suggested Duration: 5 days Universal Gravitation and General Relativity Lesson Synopsis: This lesson explores the development of Newton’s gravitational law and its application and the study of the historical development of gravity concepts, including the formal basis and predictions of Einstein’s general theory of relativity. Application of the theories will be a focus so students gain a deeper understanding of how planetary motion, satellite orbits, tides, and motion near Earth are impacted. This unit provides opportunities to distinguish between hypotheses, theories, and laws. TEKS: P.4 P.4F P.5 P.5A P.5B Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: Identify and describe motion relative to different frames of reference. Supporting Standard The student knows the nature of forces in the physical world. The student is expected to: Research and describe the historical development of the concepts of gravitational, electromagnetic, weak nuclear, and strong forces. Supporting Standard Describe and calculate how the magnitude of the gravitational force between two objects depends on their masses and the distance between their centers. Readiness Standard Scientific Process TEKS: P.2 P.2A P.2B P.2C P.2D P.2K P.3 The student uses a systematic approach to answer scientific laboratory and field investigative questions. The student is expected to: Know the definition of science and understand that it has limitations, as specified in subsection (b)(2) of this section. Know that scientific hypotheses are tentative and testable statements that must be capable of being supported or not supported by observational evidence. Hypotheses of durable explanatory power which have been tested over a wide variety of conditions are incorporated into theories. Know that scientific theories are based on natural and physical phenomena and are capable of being tested by multiple independent researchers. Unlike hypotheses, scientific theories are well-established and highlyreliable explanations, but may be subject to change as new areas of science and new technologies are developed. Distinguish between scientific hypotheses and scientific theories. Communicate valid conclusions supported by the data through various methods such as lab reports, labeled drawings, graphic organizers, journals, summaries, oral reports, and technology-based reports. The student uses critical thinking and scientific reasoning, and problem solving to make informed decisions within and outside the classroom. The student is expected to: P.3A In all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student. P.3D Explain the impacts of the scientific contributions of a variety of historical and contemporary scientists on scientific thought and society. Express and interpret relationships symbolically in accordance with accepted theories to make predictions and solve problems mathematically, including problems requiring proportional reasoning and graphical vector addition. P.3F GETTING READY FOR INSTRUCTION Performance Indicator(s): • Research and create a written report on the history of gravitational forces, including Einstein’s contributions. Use calculations to describe how the magnitude of the gravitational force between two objects depends on their masses and the distance between their centers. (P.2K; P.3D; P.5A, P.5B) 4D, 4I; 5G Key Understandings and Guiding Questions: • The universal law of gravitation formulated by Newton states that every two objects in the universe with mass are attracted to each other. ©2012, TESCCC 6 01/10/13 page 1 of Physics HS/Science Unit: 05 Lesson: 01 • — What is gravity? — In what ways does gravity hold the universe together? The history of gravity is essential to a complete understanding of its importance. Newton reasoned its general properties, Cavendish measured it, and Einstein extended it to an integrated theory of space and time. — Who are important scientists in explaining gravity, and what did they do? — What does relativity have to do with gravity? Vocabulary of Instruction: • • • • • • • • • • • • speed orbit satellite tides relativity Kepler’s laws space time continuum theory hypothesis inertial property orbital period ellipse • • • • • gravitation centripetal acceleration uniform circular motion velocity black hole Materials: Refer to Notes for Teacher section for materials. Attachments: • • • • • • • • • • Handout: Newton and the Apple (1 per student) Teacher Resource: Newton and the Apple KEY Teacher Resource: Gravity Notes Teacher Resource: Gravity, Projectile Motion, and Orbital Motion Handout: Research Questions and Rules – Presentation (1 per student) Teacher Resource: Research Questions and Rules – Presentation KEY Handout: My Solar System Lab (1 per student) Teacher Resource: My Solar System Lab KEY Handout: Problems with Gravity (1 per student) Teacher Resource: Problems with Gravity KEY Resources and References: • • “The Apple and the Moon” video: http://www.learner.org/vod/vod_window.html?pid=555 Phet simulation - “My Solar System”: http://phet.colorado.edu/simulations/sims.php?sim=My_Solar_System Advance Preparation: 1. Make certain that the software that is needed is installed. 2. Prepare attachment(s) as necessary. Background Information: Newton's three laws of motion and the universal law of gravity are landmark theories in classical physics. The universal law of gravitation describes the weakest of the fundamental forces in nature, yet it is the force that holds the universe together. The success of this law, in describing the motion of planets and stars, provides evidence that the laws of nature on Earth are universal, describing events throughout the universe. The students will learn that near Earth's surface, Newton’s gravitational law describes the gravitational attraction (weight) of objects to the Earth, but it is also the law that describes gravity as the force keeping satellites, moons, planets, and galaxies from flying apart. The historical development of ideas about gravity will begin with the legend of Newton’s falling apple and end with Einstein’s general theory of relativity, where gravity bends light and slows the passing of time. In the extreme, Einstein’s relativity predicts or accepts the possibility of science fiction-like entities of black holes, worm holes, and time travel. Since Lesson 02 is largely a study of Einstein’s special theory of relativity, the discussion of Einstein continues into the next lesson. There are no inherent safety considerations for this lesson. 009, TESCCC 09/03/11 page 2 of 6 Physics HS/Science Unit: 05 Lesson: 01 GETTING READY FOR INSTRUCTION SUPPLEMENTAL PLANNING DOCUMENT Instructors are encouraged to supplement and substitute resources, materials, and activities to differentiate instruction to address the needs of learners. The Exemplar Lessons are one approach to teaching and reaching the Performance Indicators and Specificity in the Instructional Focus Document for this unit. Instructors are encouraged to create original lessons using the Content Creator in the Tools Tab located at the top of the page. All originally authored lessons can be saved in the “My CSCOPE” Tab within the “My Content” area. INSTRUCTIONAL PROCEDURES Instructional Procedures Notes for Teacher ENGAGE – Introduction to Universal Gravitation NOTE: 1 Day = 50 minutes Suggested Day 1 Attachments: • Handout: Newton and the Apple (1 per student) • Video: “The Apple and the Moon”: http://www.learner.org/vod/vod_wind ow.html?pid=555 • Teacher Resource: Newton and the Apple KEY • Teacher Resource: Gravity Notes • Teacher Resource: Gravity, Projectile Motion, and Orbital Motion • Handout: Research Questions and Rules – Presentation (1 per student) • Teacher Resource: Research Questions and Rules – Presentation KEY 1. Use the Handout: Newton and the Apple to focus the attention of the students during the showing of the streaming video “The Apple and the Moon” from the Mechanical Universe Series. The site for the video is http://www.learner.org/vod/vod_window.html?pid=555. It is free for streaming to your class, but it may be necessary to create a login account. 2. Have students take notes and listen for the answers to specific questions. The answers could be used as a quick review of the concepts and to aid the upcoming classroom discussion. This sheet is not to be used for grading purposes. 3. After viewing the video, Ask: • What is the connection between tides, black holes, and planets orbiting the Sun? Students should arrive at the idea that it is gravity. • Is this the same gravity that causes things to fall on the Earth? (Yes) • Does gravity behave the same everywhere in the universe? Lead students to the idea that gravity is the same here and in space and that gravity laws are universal. • What is gravity? What causes gravity to attract objects to each other? Students should remember that mass is the cause of gravity. • How do we define a straight line? Various answers work, such as the shortest distance between points A & B, but point out a good answer is often the path that light travels. • Does gravity affect light? Leave this answer for the students to think about or research, but the answer is: If strong enough, it bends its path from the original path – normally, it does not. • What is a black hole? (Region of space where gravity is so strong that light cannot escape) • If light cannot escape from a black hole, does that mean that light has mass? (No) • In what ways does gravity hold the universe together? Don’t dwell on this question now, but use it as a lead-in to the discussion on general relativity. 4. Facilitate a classroom discussion on gravity. A historical overview approach is suggested, which will give some focus to student research papers. The Teacher Resource: Gravity Notes will assist with classroom discussion; the Teacher Resource: Gravity, Projectile Motion, and Orbital Motion is a companion document to the notes. 5. Distribute the Handout: Research Questions and Rules – Presentation and expectations for the research project. This will allow students to gather more information about the historical contributions of scientists. Students 009, TESCCC 09/03/11 Instructional Notes: The Mechanical Universe series is excellent, but the mathematics is often calculus-based and is displayed quickly in some videos. Preview the videos to make sure they are appropriate for the level of the students. The purpose of the Engage activity is to introduce this unit, assess prior knowledge, and concentrate on Newton’s law of gravitation. After a series of questions and informal discussion, Newton’s universal law of gravitation is detailed in a classroom discussion format and related to material studied previously. Specific questions are given for the students to research and to prepare a report. A possible outline of the “discussion” is available as “Gravity Notes”, but the Mechanical Universe video does an excellent job of covering the same ideas. Notes on Research Questions: page 3 of 6 Physics HS/Science Unit: 05 Lesson: 01 Instructional Procedures Notes for Teacher will research individually, but will be assigned groups at a later time. 6. Review the research expectations with the students, and answer any questions they may have about the project. Student groups should be encouraged to begin their research immediately. A number of the questions are at least partially answered in various sections of the lesson, including the Day 1 discussion. Misconception: • Students may think that gravitational force is the same on all falling bodies. STAAR Note: The concepts and skills explored in this lesson are addressing standards associated with the STAAR Physics assessment Reporting Category 1: Force and Motion and Reporting Category 2: Gravitational, Electrical, Magnetic and Nuclear Forces. EXPLORE – My Solar System 1. After answering any questions from yesterday’s activities, announce that today students will be conducting an exploration of Newton’s universal gravitational law through the Phet simulation “My Solar System”. 2. Divide the class into laboratory groups, and have them complete the activities of the Handout: My Solar System Lab. 3. Monitor student groups, and assist in completing the activities. 4. Lead a post-lab discussion of the questions on the exploration activity at the end of the period. 5. Review the goals for the day, and remind students to work on their research questions from the engagement activity. 009, TESCCC Suggested Day 2 Attachments: • Handout: My Solar System Lab (1 per student) • Teacher Resource: My Solar System Lab KEY Instructional Notes: The purpose of today’s activities is to gain experience with Newton’s universal law of gravitation using the Phet simulation “My Solar System” which is found at this URL: http://phet.colorado.edu/simulations/sim s.php?sim=My_Solar_System Additionally, students were to explore the following: • Newton’s gravity law properties • Henry Cavendish was the first to measure the force between two objects and confirmed Newton’s hypothesis. • Some of Kepler’s law properties: o Orbits can be elliptical. o Lower orbiting objects travel faster and have a shorter period. o The centripetal force for orbiting 09/03/11 page 4 of 6 Physics HS/Science Unit: 05 Lesson: 01 Instructional Procedures Notes for Teacher • • • EXPLAIN – Problems with Gravity 1. Provide students with the Handout: Problems with Gravity. 2. Have students work in small groups on problems. Tell them they will be sharing their methods for problem solving with the class after a specific amount of work time. 3. Have student groups share the process they used to solve each problem with the class. satellites is provided by the gravitational force. The orbits of satellites look different as viewed from different locations. The velocity of a satellite in orbit depends only upon the mass of the object being orbited. The gravitational pull is on both the satellite and the body orbited. Suggested Day 3 Attachments: • Handout: Problems with Gravity (1 per student) • Teacher Resource: Problems with Gravity KEY 4. Provide further details when needed to support student explanations, and clarify misconceptions or underdeveloped concepts. Instructional Notes: The purpose for the explanation activity is to allow students opportunities to apply concepts to real-world situations. This practice problem solving activity can be done with strong student assistance in providing guidance. ELABORATE – Research Questions Suggested Day 4 1. 2. 3. If you have not previously done so, provide students with the Handout: Research Questions and Rules – Presentation from the Engage activity. Answer any questions students may have about the project. Divide students into small study or lab groups, and have them answer the questions on the research document and put them into a form according to the guidelines. Students should have been researching the answers to the questions individually and are now compiling information with their group members. Monitor groups, and assist students in preparing the research reports. Share any additional resources you might have to help them finish. Materials: • Internet connection for students and computers Attachments: • Handout: Research Questions and Rules – Presentation (1 per student) (from previous activity) • Teacher Resource: Research Questions and Rules – Presentation KEY (from previous activity) Misconceptions: • Students may think that gravitational force acts on one object at a time. • Students may think only large objects have a gravitational force. EVALUATE – Performance Indicator Performance Indicator • Research and create a written report on the history of gravitational 009, TESCCC 09/03/11 Suggested Day 5 Attachments: • Handout: Research Questions and page 5 of 6 Physics HS/Science Unit: 05 Lesson: 01 Instructional Procedures Notes for Teacher forces, including Einstein’s contributions. Use calculations to describe how the magnitude of the gravitational force between two objects depends on their masses and the distance between their centers. (P.2K; P.3D; P.5A, P.5B) 4D, 4I; 5G 1. Remind students of behavior expectations for presentations. 2. Have student groups share their presentations with the class. 009, TESCCC 09/03/11 • Rules – Presentation (from previous activity) Teacher Resource: Research Questions and Rules – Presentation KEY (from previous activity) page 6 of 6