Applications of Newton s Laws

Transcription

1 Physical Science, Quarter 4, Unit 4.1 Applications of Newton s Laws Overview Number of instructional days: 12 (1 day = 50 minutes) Content to be learned Explain why objects resist changes in motion. Explain relationships between force, mass, and acceleration. Describe how net forces produce accelerations. Identify forces in action-reaction pairs. Predict the type of earth event (earthquake, volcano, mountain) that occurs depending on existing patterns. Essential questions Why is it more difficult to push an object starting from rest than it is to keep it going at a constant speed (frictional forces)? How does plotting the location of mountain ranges and recent earthquakes and volcanic eruptions allow us to identify existing patterns? Science processes to be integrated Make predictions. Use free-body diagrams to identify forces acting on an object and the resultant motion. Perform calculations and manipulate algebraic equations. Create and analyze models, graphs, and data tables. Identify patterns and trends in data. How can a motion graph be used to determine the magnitude and direction of the net force? 41

2 Physical Science, Quarter 4, Unit 4.1 Applications of Newton s Laws (12 days) Written Curriculum Grade-Span Expectations PS 3 - The motion of an object is affected by forces. PS3 (9-11) POC 9 Apply the concepts of inertia, motion, and momentum to predict and explain situations involving forces and motion, including stationary objects and collisions. PS3 (9-11) 9 Students demonstrate an understanding of forces and motion by 9b using Newton s Laws of Motion and the Law of Conservation of Momentum to predict the effect on the motion of objects. PS3 (9-11) POC+ INQ 8 Given information (e.g., graphs, data, diagrams), use the relationships between or among force, mass, velocity, momentum, and acceleration to predict and explain the motion of objects. PS3 (9-11)- 8 Students demonstrate an understanding of forces and motion by 8a predicting and/or graphing the path of an object in different reference planes and explain how and why (forces) it occurs. ESS1 - The earth and earth materials as we know them today have developed over long periods of time, through continual change processes. ESS1 (9-11) INQ+POC 1 Provided with geologic data (including movement of plates) on a given locale, predict the likelihood for an earth event (e.g., volcanoes, mountain ranges, islands, earthquakes). ESS1 (9-11) 1 Students demonstrate an understanding of processes and change over time within earth systems by 1a plotting the location of mountain ranges and recent earthquakes and volcanic eruptions to identify any existing patterns. Clarifying the Standards Prior Learning In grades K 4, students predicted the direction of motion. Students also have experience describing the motion of objects if force is applied. They have demonstrated an understanding of force by describing that different amounts of force can change direction/speed of an object in motion. Students also have experience with magnets, observing how magnetic strength is sometimes stronger or weaker. 42

3 Physical Science, Quarter 4, Unit 4.1 Applications of Newton s Laws (12 days) In grades 5 6, students learned that forces are pushes and pulls. Forces were explained as causing changes in either speed or direction of motion. They also learned how electric currents and magnets exert forces on each other. In grades 7 8, students learned that it is unbalanced force that causes acceleration. They can describe and graphically represent the amount of acceleration as proportional to the unbalanced force. They also learned to differentiate between mass and weight. In grade 9, unit 3.3 Forces and Motion, students were introduced to Newton's laws, including definitions of force, mass, weight, and acceleration at a basic qualitative level. Current Learning The appropriate level of instruction for this unit of study is reinforcement. Since this will be the last exposure to this content, instruction will need to continue to drill-and-practice. Instruction that covers predicting where earthquakes and volcanoes will occur should begin with the reinforcement level of instruction. The drill-and-practice level of instruction will be used when completing problems based on Newton s laws and exemplifying their connection to earth science. Drill-and-practice instructional activities are key to students being able to manipulate algebraic equations (when the mathematical prior knowledge is available). Students should be aware that energy transfers occur all the time. Students must identify and follow the specific transfers of energy in a given situation. In this unit, students explain why objects resist changes in motion. They explain relationships between force, mass, and acceleration, including the relationship to action and reaction pairs, as well as describing how forces create acceleration. Students apply Newton s laws to explain the movement of plates and predict which types of earth events will occur depending on the existing patterns. Students create and use free-body diagrams to identify forces acting on an object and the resultant motion (planetary and star motion). Students learn to identify forces that act on real-life objects (e.g., cars and vehicles, sports equipment, and mountain ranges, etc.) and incorporate them into free-body diagrams. Students also learn to use these diagrams in order to calculate the net force and acceleration of the object. The Science Processes to be Integrated above are easily incorporated into these types of activities. Friction, as a real-life force, will also be introduced. Students identify sources of friction (e.g., boat in water, skateboard on road), describe the effect of friction on a moving object, and suggest ways to reduce friction in real-life mechanical systems. One way this unit can be taught is through the application of forces. It could be used in conjunction with earth science or astronomy concepts and discussing the force s interactions within these processes. For example, instruction about plate tectonics can focus on forces that cause the slow movement of crustal movement or how earthquakes are the result of forces within the crust that build and result in rapid movement within the crust. Another way to approach this unit is to focus on a particular set of forces. For example, students can describe all of the forces involved when a box is being dragged across different types of surfaces. Free-body diagrams could be drawn of the plates, reinforcing both ideas. One could emphasize the basis of motion as the transfer of energy, an essential running theme in all of physics. To this point, students have learned the relationship between force, mass, and acceleration. Students apply these concepts to a series of inquiry activities. This unit will allow students to extend their knowledge of Newton s laws, and how they relate to plate tectonics. Students have learned about forces within the earth that contribute to plate movement, and the forces responsible for the orientation of our universe. Students explore net forces and predict the resulting acceleration of an object. 43

4 Physical Science, Quarter 4, Unit 4.1 Applications of Newton s Laws (12 days) Future Learning Students will use this knowledge in future units by applying their learning of how to manipulate algebraic equations. The ability to manipulate algebraic equations is an essential part to being able to do nearly all advanced (higher-order thinking) problems. Students will also be able to use their knowledge of analyzing graphs in studying the relationship between distance-time, velocity-time, and acceleration-time graphs. Students will be able to interpret charts and other graphic information in order to logically predict future event. Students will use this knowledge of algebraic manipulation in their future chemistry course. The topic of stoichiometry relies heavily on a student s ability to balance and manipulate equations. In mathematics, chemistry, and biology students will use their knowledge of analyzing graphs of all nature variables to show correlation between variables. Additional Findings Crust sections move slowly, pressing against each other, and pulling apart in other places. Ocean floor plates may slide under continental plates. The surface area of these plates may fold causing mountain ranges. Molten rock may well up between separating plates to create new ocean floor, such as mountains and islands. (Benchmarks for Science Literacy, p. 74) Students need to understand that graphs show patterns such as trends and rates of change. In addition, students should be aware that a graph is a way to represent data, and can be used to make claims, provide evidence, and make predictions. (Atlas of Science Literacy, p. 115) In most familiar situations, frictional forces complicate the description of motion, although the basic principles still apply. (Science for All Americans p. 53; Atlas, Vol. 1, p. 63) Students tend to call the active actions forces, but do not consider passive actions as forces. (Benchmarks, p. 339) In an AAAS assessment, 51% of students had the misconception that a constant force is needed to keep an object moving at constant speed. Also, 46% of students believe that a constant force produces a constant speed. (AAAS Science Assessment website, retrieved on May 9, 2011.) Typically, students think that forces are things that make things happen or create change. Descriptions often include energy, momentum, pressure, power, and strength. (Benchmarks, p. 339) Students add forces without considering the direction of the forces, i.e., they add absolute values of the forces (AAAS Project 2061) Forty-five percent of students who participated in the AAAS Project 2061 assessment thought that earth's plates cannot bend and that mountains form by the piling up of pieces of rock (AAAS Project 2061). Several researches stressed the importance of paying attention to Newton s third law in order to help people appreciate that force is not a property of an object. Force is a characteristic of action between objects. Minstrell proposes offering bridges between prior ideas and science ideas, such as giving many examples to make the point. (Making Sense of Secondary Science, p. 150) 44

5 Physical Science, Quarter 4, Unit 4.2 Projectile Motion Overview Number of instructional days: 12 (1 day = 50 minutes) Content to be learned Predict the path of an object in different reference planes. Explain the forces involved in projectile motion. Graph the path of an object in different reference planes. Use quantitative representations to explain the path of a projectile. Use models, illustrations, and graphs to quantitatively explain the path of an object, which has horizontal and freefall motion. Essential questions How can the range of a projectile be predicted? How can models be used to quantitatively represent the trajectory of a projectile? What kind of information would be needed to accurately graph the path of objects in different reference planes? Science processes to be integrated Make predictions. Observe, measure, and draw conclusions. Create and analyze models, graphs, and data tables. Identify patterns and trends in data. Use free-body diagrams to model the motion of a projectile. Perform calculations and manipulate algebraic equations. Why are the vertical and horizontal motions of a projectile independent of each other? Why does a horizontally fired bullet hit the ground at the same time as a bullet dropped from the same height? 45

6 Physical Science, Quarter 4, Unit 4.2 Projectile Motion (12 days) Written Curriculum Grade-Span Expectations PS 3 - The motion of an object is affected by forces. PS3 (9-11) POC+ INQ 8 Given information (e.g., graphs, data, diagrams), use the relationships between or among force, mass, velocity, momentum, and acceleration to predict and explain the motion of objects. PS3 (9-11)- 8 Students demonstrate an understanding of forces and motion by 8a predicting and/or graphing the path of an object in different reference planes and explain how and why (forces) it occurs. PS3 (Ext)- 8 Students demonstrate an understanding of forces and motion by 8bb using a quantitative representation of the path of an object which has horizontal and free fall motion. 8cc by modeling, illustrating, graphing, and quantitatively explaining the path of an object, which has horizontal and free fall motion. e.g. football, projectile. Clarifying the Standards Prior Learning In grades K 2, students were exposed to motion by predicting and describing the motion of an object when a force was applied to it. Students began by predicting the direction and later describing the changes in position relative to other objects. In grades 3 5, students used data and graphs to compare the relative speeds of objects. Students have explained that changes in speed or direction in motion are caused by forces. In grades 6 8, students measured distance and time to determine speed through scientific inquiry. Students produced graphs from their measurements of distance and time to represent the motion of an object. They also manipulated the formula speed = distance/time to solve for any one of the three variables. Students should be able to distinguish between speed, velocity, and acceleration. Current Learning The developmental level of instruction is necessary for projectile motion, which is complicated due to the fact that it involves motion in two directions (the object accelerates as it falls towards the earth and stays constant in the horizontal direction). Graphing is reinforced by creating graphs of projectile motion. In this unit, educators teach students how to predict the path of an object in different reference planes. They explain the forces involved in projectile motion and graph the path of an object in different 46

7 Physical Science, Quarter 4, Unit 4.2 Projectile Motion (12 days) reference planes. Also they use quantitative representations to explain the path of a projectile. Models, illustrations, and graphs are used to explain the path of an object that has horizontal and freefall motion. Students make predictions on the path of a projectile. They also observe, measure, and draw conclusions on projectile motion. Students create and analyze graphs and models representing projectile motion. Also students will identify patterns and trends in data. They use free-body diagrams to model the motion of a projectile as well as perform calculations based on data. This unit consists of notes on projectile motion as well as the introduction to the following equations: dx = vxt, dy = 1/2gt2, vy= g x t. The students manipulate these three equations to calculate various practice problems. A marble launcher can be used to demonstrate what an object looks like when it is shot and follows a projectile path. The launcher can be used to demonstrate a projectile shot off a ledge horizontally as well as at an angle. On-demand tasks are used to reinforce the concepts of projectile motion. Students are able to graph the motion of a projectile. Students have experience solving problems involving horizontal and freefall motion independently. These two motions are now combined to predict, graph, and analyze projectile motion. In this unit, the formulas are modified to distinguish between the horizontal (x) and vertical (y) components of the projectile s motion. Future Learning The concepts of force, gravity, and projectiles will lead into the unit on Universal Gravitation (although the calculations are very different, many of the concepts of orbital motion rely on a basic understanding of projectiles. Students may use their knowledge of projectile motion in future courses that deal more specifically with motion. For instance, a forensics class may do a unit on accident reconstruction or gunshot trajectories. Additional Findings Students need to understand that graphs show patterns such as trends and rates of change. In addition, students should be aware that a graph is a way to represent data, and can be used to make claims, provide evidence, and make predictions (Atlas of Science Literacy, p. 115). A fired object initially moves in the direction of firing. Only after some impetus has been used up, can gravity act and the object fall towards the ground (McCloskey, 1983a). If an object is moving, then there must be a force in the direction of motion (Tao & Gunstone, 1999). When asked to predict the motion of two balls, one rolled off a cliff and the other dropped simultaneously from the same height, most students answered incorrectly. The most common incorrect answer, given by 40% of the students, was that the dropped ball was travelling a shorter path so it would reach the ground first. ( website, Most students treated dropping and firing as different situations and not as different examples of projectile motion. However, students who believed that a fired object gain impetus when fired tended also to believe that objects dropped from a moving carrier gained no impetus and so dropped straight down. ( website, 47

8 Physical Science, Quarter 4, Unit 4.2 Projectile Motion (12 days) A review of the research literature on cognitive conflict suggested that it would be most successful when students are made acutely aware of their misconceptions and students reflect on projectile motion in a variety of familiar contexts (Prescott, A. E. (2004). Student understanding and learning about projectile motion in senior high school. Unpublished doctoral thesis, Macquarie University, Sydney). 48

9 Physical Science, Quarter 4, Unit 4.3 Universal Gravitation Overview Number of instructional days: 6 (1 day = 50 minutes) Content to be learned Explain the effect of mass on the gravitational force between objects. Explain the effect of distance between two objects on the gravitational force between them. Explain the role of gravity in the process of star formation. Describe the role of gravity in the lifecycle of stars. Essential questions How do changes in the mass of an object and/or the distance to another object affect the force of gravity? How is gravity involved in the formation and lifecycle of stars? Science processes to be integrated Make predictions. Create and analyze models. Identify patterns and trends in a system. Use free-body diagrams to model the gravitational attraction between two objects. Perform calculations and manipulate algebraic equations. How can the Universal Gravitation Law be used to prove whether there is a stronger gravitational force between the earth and the moon or between the sun and the moon? 49

10 Physical Science, Quarter 4, Unit 4.3 Universal Gravitation (6 days) Written Curriculum Grade-Span Expectations PS 3 - The motion of an object is affected by forces. PS3 (9-11) POC 9 Apply the concepts of inertia, motion, and momentum to predict and explain situations involving forces and motion, including stationary objects and collisions. PS3 (9-11) 9 Students demonstrate an understanding of forces and motion by 9a explaining through words, charts, diagrams, and models the effects of distance and the amount of mass on the gravitational force between objects (e.g. Universal Gravitation Law). ESS3 - The origin and evolution of galaxies and the universe demonstrate fundamental principles of physical science across vast distances and time ESS3 (9-11) POC+SAE 8 Explain the relationships between or among the energy produced from nuclear reactions, the origin of elements, and the life cycle of stars. ESS3 (9-11) 8 Students demonstrate an understanding of the life cycle of stars by 8a relating the process of star formation to the size of the star and including the interaction of the force of gravity, fusion, and energy release in the development of the star identifying and describing the characteristics common to most stars in the universe. 8b Describing the ongoing processes involved in star formation, their life cycles and their destruction. Clarifying the Standards Prior Learning In grades K 4, students gained some hands-on experience exploring gravity and falling objects. They also demonstrated understanding of the motion and position of planets, the sun, and stars. In grades 5 6, students recognized that forces cause changes in speed or direction of motion, but did not have any GSE targets relating to stars or the sun. In grades 7 8, students began to relate motion to mathematical formulas (s=d/t) and learned to differentiate between mass and weight. They learned that sunlight is made up of a mixture of many colors, which will lead in this unit to a discussion of how scientists know about the composition of stars. They also learned that the universe contains billions of galaxies, that each galaxy contains billions of stars, and that gravity causes the forces between astronomical objects. They learned to qualitatively describe the relationship between distance and gravitational force. 50

11 Physical Science, Quarter 4, Unit 4.3 Universal Gravitation (6 days) Current Learning This unit extends knowledge of gravitational forces by introducing the quantitative representation. Instruction will begin at the level of reinforcement and continue through drill-and-practice. To this point, students have only qualitatively described the relationship between mass, distance, and gravitational force. Students are aware that stars make up the structure of the universe and exist in different sizes. This unit concentrates on star formation and the lifecycle of stars as well as gravity s role in that process. Drilland-practice will be used to complete universal gravitation problems. In this unit, students explain the effect of mass and separation distance on the gravitational force between objects. Students use the universal law of gravitation equation to solve for the force of gravity between two objects. They explain the role of gravity in the process of star formation and the lifecycle of stars. Students make predictions based on data, models, and diagrams pertaining to universal gravitation. They use free-body diagrams to model the gravitational attraction between two objects. Students perform calculations and manipulate algebraic equations to solve the gravitation problems. They also need to master the use of multiplying and dividing by exponential numbers (written in scientific notation), which was originally presented to them in the electrostatics unit involving Coulombs Law. Students are introduced to the concept of universal gravitation and are required to complete problems using the universal gravitation equation. Demonstrations from various computer programs could be used to help students understand the concepts in this unit of study. Students are required to diagram two-body systems and calculate the force of gravity between them. Students describe what happens during the formation of stars, for example, when the mass increases to the point where gravity becomes so great that atoms are compressed to a point of fusion (not yet taught concept) and the stars life begins. In this unit, students extend their knowledge of universal gravitation by directly applying a mathematical formula to the concept. In previous courses, students only looked at the conceptual relationships between mass and distance. Future Learning Students will use this knowledge in the upcoming unit on mechanical energy and energy conservation. Once presented with the concept of kinetic energy, students will be shown that work done parallel to the force of gravity gives or reduces an objects potential energy. Understanding of the law of universal gravitation will finally answer the yearlong question of why the acceleration due to gravity on the surface of the earth is 9.8 m/s^2. In this unit, students experience a large variety of problems involving scientific notation. This practice of multiplying and dividing by numbers too big or too small for standard notation, will be critical in chemistry when dealing with moles and masses of elementary particles. Also, in students math classes, they will frequently use scientific notation, eventually leading to exponential functions and graphs. Additional Findings Every planet has mass and so every planet exerts a gravitational force on nearby objects. We say that planets have gravity. However, what we really mean is that there is a gravitational force of attraction between the planet and a person standing on the planet's surface. This force depends on the visitor's mass, the planet's mass, and the planet's radius. Accordingly, people have different weights on different planets. (Montana.edu website: 51

12 Physical Science, Quarter 4, Unit 4.3 Universal Gravitation (6 days) Students of all ages may hold misconceptions about the magnitude of the earth's gravitational force. Even after a physics course, many high school students believe that gravity increases with height above the earth's surface [Gunstone, R., White, R. (1981). Understanding of gravity. Science Education, 65, ] Many high school students are not sure whether the force of gravity would be greater on a lead ball than on a wooden ball of the same size. [Brown, D., Clement, J. (1992). Classroom teaching experiments in mechanics. In Duit, R. (Ed.), Research in physics learning: Theoretical issues and empirical studies. pp ] High school students also have difficulty in conceptualizing gravitational forces as interactions. In particular, they have difficulty in understanding that the magnitudes of the gravitational forces that two objects of different mass exert on each other are equal. [Brown, D., Clement, J. (1992). Classroom teaching experiments in mechanics. In Duit, R. (Ed.), Research in physics learning: Theoretical issues and empirical studies, pp ] There is a notion that appears to bound up with pupils common belief that gravity is associated with air and that where there is no air, there is no air. (Making Sense of Secondary Science, p. 166) Students need to understand that gravity is fundamentally different from strong electromagnetic and weak forces. For one thing is it much weaker than they are. (Science Matters: Achieving Scientific Literacy, p. 163) Several researches stressed the importance of paying attention to Newton s Third Law in order to help people appreciate that force is not a property of an object. Force is a characteristic of action between objects. Minstrell proposes offering bridges between prior ideas and science ideas, such as giving many examples to make the point. (Making Sense, p. 150) References: Online Physics Simulations. 52

13 Physical Science, Quarter 4, Unit 4.4 Momentum and Mechanical Energy Overview Number of instructional days: 15 (1 day = 50 minutes) Content to be learned Describe or diagram the changes in energy (transformation) that occur in different systems. Identify, measure, calculate and analyze qualitative relationships associated with energy transfer or energy transformation. Identify, measure, calculate, and analyze quantitative relationships associated with energy transfer or energy transformation. Explain the Law of Conservation of Energy as it relates to the efficiency (loss of heat) of a system. Qualitatively determine the efficiency of a given system. Use the Law of Conservation of Momentum to predict the effect on the motion of objects. Essential questions How does the Law of Conservation of Energy apply to the efficiency of the system? How should calculations be used to determine and predict the transformation of energy in a system? What is meant by energy lost in a system? Science processes to be integrated Make predictions. Create and analyze models. Identify patterns and trends in a system. Use models. Perform calculations and manipulate algebraic equations. How can you use the Law of Conservation of Momentum to predict the effect on the motion of an object? What should be included in a diagram that shows how changes in energy occur? 53

14 Physical Science, Quarter 4, Unit 4.4 Momentum and Mechanical Energy (15 days) Written Curriculum Grade-Span Expectations PS 2 - Energy is necessary for change to occur in matter. Energy can be stored, transferred, and transformed, but cannot be destroyed. PS2 (9-11) POC+SAE -5 Demonstrate how transformations of energy produce some energy in the form of heat and therefore the efficiency of the system is reduced (chemical, biological, and physical systems). PS2 (9-11)-5 Students demonstrate an understanding of energy by 5a describing or diagramming the changes in energy (transformation) that occur in different systems (e.g. chemical = exo and endo thermic reactions, biological = food webs, physical = phase changes). PS2 (Ext) 5 Students demonstrate an understanding of energy by 5aa Identifying, measuring, calculating and analyzing qualitative and quantitative relationships associated with energy transfer or energy transformation. 5b explaining the Law of Conservation of Energy as it relates to the efficiency (loss of heat) of a system. 5bb quantitatively determining the efficiency of a given system. PS 3 - The motion of an object is affected by forces. PS3 (9-11) POC 9 Apply the concepts of inertia, motion, and momentum to predict and explain situations involving forces and motion, including stationary objects and collisions. PS3 (9-11) 9 Students demonstrate an understanding of forces and motion by 9b using Newton s Laws of Motion and the Law of Conservation of Momentum to predict the effect on the motion of objects. Clarifying the Standards Prior Learning In grades K 4, students were exposed to the concepts of heat energy, and to basic concepts of motion. In grades 5 6, students learned to differentiate among the properties of various forms of energy, and explained how energy can be stored in various ways (e.g., batteries, springs, height). They also described sound as a transfer of energy, and learned to identify real-world applications where heat energy is transferred. 54

15 Physical Science, Quarter 4, Unit 4.4 Momentum and Mechanical Energy (15 days) In grades 7 8, students learned that changing heat energy affects the motion and arrangement of molecules. They could use real-world examples to explain the transfer of potential to kinetic energy, and constructed models to explain energy transformations from one form to another (e.g., electrical to light energy in a light bulb). They could explain that, while energy can be stored, transferred, or transformed, the total amount is always conserved. In terms of motion, students learned to differentiate between speed, velocity, and acceleration, and that forces cause changes in the speed or direction of motion of an object. In prior units, students have recently completely units on motion, position and velocity graphs, acceleration, and forces and Newton's laws. They have also been discussing energy as an underlying theme for this course, including concepts of heat energy, sound and electromagnetic energy, and electrical energy throughout various units. Current Learning Students have been exposed to this content for multiple years. They have not been introduced to the Law of Conservation of Momentum; therefore, when initially introduced this portion of the unit should be taught at the developmental level. Later, when dealing with momentum problems, the instructional level will be drill-and-practice; the students will multiple exposures to this content in order to fully grasp the conservation of momentum equation. Students describe or diagram the changes in energy (transformation) that occur in different systems. They identify, measure, calculate, and analyze qualitative and quantitative relationships associated with energy transfer or energy transformation. In addition, students use the Law of Conservation of Energy as it relates to the efficiency (loss of heat) of a system and qualitatively determine the efficiency of a given system. Finally, they identify variables that cause inefficiencies in a system. The Law of Conservation of Momentum is used to predict the effect on the motion of objects. Students make predictions and form hypotheses based on models and diagrams in addition to drawing conclusions. They solve momentum and efficiency problems by manipulating algebraic equations. Students will analyze and create models of situations involving momentum. Students will also be identifying patterns and trends of a system based on the concept of momentum. Students will identify that the sun is a giant, hot ball of gas held together by gravity. The sun is mediumsized compared with other stars in the universe. Gravity squeezes the density of a star so tightly in the core that the electrons are stripped away and the bare nuclei of atoms almost touch each other. Nuclear fusion occurs. In the process, huge amounts of energy are given off. Because of its mass, the sun s gravitational force is strong enough to hold the entire solar system in orbit. Future Learning Students will use this knowledge in future courses such as forensics if a unit is done involving accident reconstruction of a vehicle of vehicles. The ability to understand the difference between elastic and inelastic collisions will be important in understanding the collision of anything ranging from macroscopic objects such as cars to microscopic objects such as particles. 55

16 Physical Science, Quarter 4, Unit 4.4 Momentum and Mechanical Energy (15 days) Additional Findings Some students hold a notion of a source of energy in some things. Only the things with energy in them were thought capable of making things happen. (Making Sense of Secondary Science, p. 144). A misconception among students exists that energy does not exist with stationary objects. The outward display of movement was thought of as the energy (energy was thought of as doing ). (Making Sense, p. 145) Many students use the words force and energy synonymously. (Making Sense, p. 145) Furthermore, AAAS reports that 58% of high school students think that energy can be transformed into a force. ( in this unit of study? [Atlas of Science Literacy, Benchmarks for Science Literacy, National Science Education Standards (content standards)] Students seem to have difficulty understanding the transformation of energy from motion to heat, especially in cases with no obvious temperature increase (Benchmarks. p. 338). The following are some commonly held student misconceptions: The gravitational potential energy of an object depends upon the path the object takes to get to the distance above the reference point. (Singh & Rosengrant, 2001, 2003; Herrmann-Abell & DeBoer, 2010) An object has gravitational potential energy only at the edge of a cliff or table but not at some distance from the edge. (Kruger, 1990) Only objects that are stretched have elastic energy. Compressed objects do not have elastic energy. (AAAS Project 2061, n.d.) Energy can be transformed into a force. (AAAS Project 2061, n.d.) An object has energy within it that is used up as the object moves (Brook & Driver, 1984; Kesidou & Duit, 1993; Loverude, 2004; Stead, 1980). When one object pushes or pulls on another object, a force, not energy, is transferred. (AAAS Project 2061, n.d.) Energy cannot be transferred from one object to another. (AAAS Project 2061, n.d.) 56