FF: Fundamental Forces & Fields

Activities & Reader (ISBN 0-7872-5412-6, 207 pages)

How to Use this Book    xv

Acknowledgments    xvii

Activities

  • FF·1 - Exploring Models of Electromagnetism    1
  • FF·2 - Using a Model to Interpret, Explain, and Predict    7
  • FF·3 - Investigating Electrical Properties of Materials    13
  • FF·4 - Reasoning with a Model for Electrical Interactions    17
  • FF·5 - Exploring the Magnetic Interaction    21
  • FF·6 - Modeling the Magnetic Properties of Materials    25
  • FF·7 - Modeling the Magnetic Properties of Moving Charges    29
  • FF·8 - Reasoning with a Model for Magnetic Interactions    35
  • FF·9 - Exploring the Gravitational Interaction    39
  • FF·10 - Exploring the Idea of Weight    43
  • FF·11 - Distinguishing Mass and Weight    47
  • FF·12 - Modeling Universal Gravitation    51
  • FF·13 - Using a Mathematical Model for the Electric Force    55
  • FF·14 - Applying Coulomb's Law to Continuous Distributions of Charge    59
  • FF·15 - Estimating Electric Forces Using Coulomb's Law    65
  • FF·16 - Reasoning with Coulomb's Law    69
  • FF·17 - Developing an Empirical Force Law for Magnets    73
  • FF·18 - Using the Universal Law of Gravitation    79
  • FF·19 - Applying Universal Gravitation to Large-Scale Objects    83
  • FF·20 - Reasoning with Universal Gravitation    87
  • FF·21 - Mapping Magnetic Fields    91
  • FF·22 - Representing the Electric Field    97
  • FF·23 - Representing the Electric Field as a Vector Field    101
  • FF·24 - Investigating the Gravitational Field    107
  • FF·25 - Representing Vector Fields Using Field Line Diagrams    111
  • FF·26 - Applying Newton's Laws    117
  • FF·27 - Applying Work and Energy Ideas    121
  • FF·28 - Solving Problems Using Work and Energy Ideas    127
  • FF·29 - Summarizing and Structuring the Fundamental Forces    131

Reader: Fundamental Forces and Fields

  • 0. Introduction    R1
    • what is meant by a fundamental force    R1
    • a list of the fundamental forces    R1
    • some examples of what the fundamental forces are responsible for    R1
    • the organization of the Reader    R1
  • 1. QUALITATIVE DESCRIPTIONS OF FUNDAMENTAL FORCES    R1-20
    • 1.1. Modeling interactions    R2
      • what is meant by the term model    R2
      • goal of a model    R2
      • graphic representation of modeling    R2
    • 1.2. Electric phenomena    R2,3
      • examples of electric phenomena    R2
      • table showing how rubbed objects interact with each other    R3
      • introducing electric charge to explain pattern of electric phenomena    R3
      • defining which objects are said to be positive, which are negative, and which are neutral    R3
    • 1.3. Reasoning about electric interactions    R4
      • an example showing how we can predict the behavior of something    R4
      • an example showing the limitations of our current model    R4
    • 1.4. A simplified model of electric interactions    R4-6
      • goal of our simplified model    R4
      • assumption 1: All matter is made up of sub-microscopic particles    R5
      • assumption 2: These particles have mass and charge    R5
      • assumption 3: "Like" charges repel; "opposite" charges attract; neutral particles do not interact    R5
      • assumption 4: Everyday objects are neutral    R6
      • assumption 5: Charges can be transferred    R6
      • assumption 6: Electric interactions occur when one or both objects have excess charge    R6
      • assumption 7: Charge is conserved    R6
      • assumption 8: The mass of sub-microscopic particles is very small    R6
      • assumption 9: When styrofoam is rubbed with fur, the fur is defined to be positive, and the styrofoam is defined to be negative    R6
    • 1.5. Applying the simplified model of electric interactions    R7
      • An example showing how the model can predict the behavior of something    R7
    • 1.6. The atomic model of matter    R7,8
      • types of charge on the proton, neutron, and electron    R7
      • how the atomic model will and will not be used    R8
    • 1.7. A model of the electrical properties of materials    R8,9
      • goal of our model of electrical properties of materials    R8
      • assertion 1: Only electrons can be transferred by rubbing    R8
      • assertion 2: Excess electrons on a conductor flow easily    R8
      • why some electrical demonstrations give inconsistent results    R8
      • assertion 3: Excess electrons on an insulator do not flow very easily    R9
      • assertion 4: Some electrons in a conductor are relatively free to move    R9
      • conductors exchange electrons on contact    R9
      • assertion 5: Most electrons in an insulator are not relatively free to move    R9
      • assertion 6: The strength of the electric force depends on charge separation    R9
    • 1.8. Applying the atomic model of electric interactions    R10,11
      • explaining why neutral objects are attracted to charged objects    R10
      • predicting the charges on pie plates    R11
    • 1.9. Magnetic phenomena    R11,12
      • what is meant by a permanent magnet    R11
      • what is meant by the poles of a magnet    R11
      • what is meant by the North (N) and South (S) poles of a magnet    R11
      • table showing how different materials interact magnetically    R12
      • other properties of interacting materials    R12
    • 1.10 Modeling the magnetic interaction    R12-14
      • what is meant by a nanomagnet    R13
      • assumption 1: All matter is made up of tiny nanomagnets    R13
      • assumption 2: "Like" poles repel; "opposite" poles attract    R13
      • assumption 3: Every material's nanomagnets have a characteristic strength    R13
      • what is meant by magnetic materials    R13
      • assumption 4: The interaction of two nanomagnets depends on their strengths    R13
      • assumption 5: The interaction of two nanomagnets depends on their separation    R13
      • what is meant by non-magnetic materials    R13
      • how these assumptions are applied to different materials    R13
      • rough depictions of the nanomagnets in non-magnetic materials, magnetic materials, and permanent magnets    R14
      • what is meant by a magnetic domain    R14
    • 1.11 Applying our simplified model of magnetic interactions    R14
      • Examples of how to apply this model of magnetic interactions    R14
    • 1.12 An atomic model of magnetic interactions    R15
      • reasons we need to go to the atomic model    R15
      • two moving charges are needed for the magnetic interaction    R15
      • how to go from moving charges to nanomagnets    R15
    • 1.13 Applying the atomic model of magnetic interactions    R16
      • one more assumption: the strength of a nanomagnet is due primarily to an atom's orbiting electrons    R16
      • examples of how to apply the atomic model of magnetic interactions    R16
    • 1.14 "Local" gravitation    R17,18
      • what is meant by local gravitation    R17
      • how we know that gravitation is caused by the Earth    R17
      • what is meant by "local" gravitation on the Moon    R18
    • 1.15 Weight    R18
      • how weight might appear to be different for different observers    R18
      • definition of the term weight    R18
      • why a scale sometimes cannot be used to determine weight    R18
      • why air has weight    R18
    • 1.16 Mass vs. weight    R19
      • differences between mass and weight    R19
    • 1.17 "Universal" gravitation    R19,20
      • what is meant by Universal gravitation    R19
      • gravitational force as a function of position assuming the Earth has a uniform density    R19
      • comparison of the gravitational forces exerted by the Earth and the Moon    R20
      • why the local gravitational constant on the Moon is 1/6 that on the Earth    R20
      • summary of gravitation    R20
  • 2. MATHEMATICAL DESCRIPTIONS OF FUNDAMENTAL FORCES    R21-33
    • 2.1. Coulomb's law for electric forces    R21,22
      • what is meant by a point charge    R21
      • mathematical description of Coulomb's law    R21
      • how to find the direction of the electric force    R21
      • MKS unit of charge (the Coulomb, C)    R22
      • charges of the proton and electron    R22
      • an example of how to apply Coulomb's law    R22
    • 2.2. The Superposition Principle    R22,23
      • why we need the Superposition Principle    R22
      • verbal description of the Superposition Principle    R22
      • an example showing how to apply the Superposition Principle    R23
    • 2.3. Applying Coulomb's law to non-point objects    R24
      • force law when objects are far apart    R24
      • how to treat objects close together    R24
    • 2.4. Reasoning with Coulomb's law    R25,26
      • a convenient unit of charge is the microCoulomb (µC)    R25
      • 3 examples showing how to reason using Coulomb's law    R25,26
    • 2.5. Universal law of gravitation    R27,28
      • mathematical description of the Universal law of gravitation    R27
      • how to find the direction of the gravitational force    R27
      • an example showing how to apply the Universal law of gravitation    R27
      • an example showing how to apply the Superposition Principle    R28
    • 2.6. Applying Universal gravitation to non-point objects    R28,29
      • applying Universal gravitation when objects are far apart    R28
      • applying Universal gravitation when an object is close to a celestial body    R28,29
      • what is meant by a shell    R28
      • force law when object is outside the mass shell    R29
      • force law when object is inside the mass shell    R29
      • how to apply these results to celestial bodies such as the Earth and Moon    R29
    • 2.7. Astronomical data    R30
      • mass, average radius, average density, g on its surface, average orbital radius, and orbital period for the Earth, the Moon, and the Sun    R30
      • an example of how to use astronomical data    R30
    • 2.8. Deciding how to apply the Universal law of gravitation    R30,31
      • 3 general methods for applying the Universal law of gravitation    R30,31
      • an example showing how these methods apply to 6 situations    R31
    • 2.9. Reasoning with Universal gravitation    R32,33
      • examples showing how to reason using Universal gravitation    R32,33
    • 2.10 The magnetic interaction    R33
      • why we cannot provide a mathematical description of the magnetic interaction    R33
      • some features you should still know about the magnetic interaction    R33
  • 3. FIELDS    R34-45
    • some of the different ways the term field is used    R34
    • 3.1. Scalar vs. vector fields    R34
      • what is meant by a scalar field    R34
      • what is meant by a vector field    R34
      • temperature is a good example of a scalar field    R34
      • velocity of air currents is a good example of a vector field    R34
      • vector field diagram for air currents in a certain region of space    R34
    • 3.2. Fields for fundamental forces    R35
      • why we introduce fields for fundamental forces    R35
      • how a fundamental field is defined: in terms of the force exerted on an object    R35
      • what creates what types of fields    R35
    • 3.3. The electric field    R36
      • force on point charge q due to electric field E    R36
      • definition of the electric field    R36
      • using Coulomb's law to find the electric field created by a point charge    R36
      • finding the direction of the electric field    R36
      • how the mutual forces can be the same even though the fields are different    R36
    • 3.4. Electric field for multiple point charges    R37
      • an example of how to find the electric field for two point charges    R37
      • vector field diagrams for the "dipole" and "dicharge" distributions of charge    R37
    • 3.5. Electric field for a spherical shell of charge    R38
      • electric field inside a shell of charge    R38
      • electric field outside a shell of charge    R38
      • finding the direction of the electric field outside a shell of charge    R38
      • an example showing how to find the electric field on a rubber ball    R38
    • 3.6. The gravitational field    R39
      • why we use the same symbol for "local" and "Universal" gravitation    R39
      • definition of the gravitational field    R39
      • gravitational field created by a point mass    R39
      • how to find the direction of the gravitational field    R39
    • 3.7. Gravitational field for non-point masses    R39,40
      • using shells to find the gravitational field for a celestial body    R39
      • sketch of gravitational field strength g vs. distance from the center of the Earth    R40
      • finding and verifying the location between the Earth and the Moon where the gravitational field is zero    R40
    • 3.8. The magnetic field    R41
      • why we use a compass needle to determine the direction of the magnetic field    R41
      • magnetic field for a long, straight wire    R41
      • magnetic field for a loop of wire    R41
    • 3.9. Finding the magnetic field for other arrangements of current-carrying wire    R42
      • magnetic field for two parallel wires, with currents moving in opposite directions    R42
      • magnetic field for a coil of wire    R42
    • 3.10 Force on a point charge moving through a magnetic field    R42,43
      • diagram showing the orientations of the velocity v, magnetic field B, and magnetic force Fm    R42
      • 2 mathematical expressions for the magnetic force on charge q    R43
      • finding the direction of the magnetic force    R43
      • why we cannot write an expression for the magnetic field B created by a moving point charge    R43
    • 3.11 Limitations of vector field diagrams    R43
      • many reasons why vector field diagrams are sometimes not the best way to represent fields    R43
      • an example using the "dipole" arrangement of charges    R43
    • 3.12 Field line diagrams    R44
      • what is meant by a field line    R44
      • how to find the direction of the vector field using a field line    R44
      • field line diagrams are 3 dimensional    R44
      • drawing showing the field lines near a positive point charge    R44
      • how to find the comparative strength of the vector field using the density of field lines    R44
      • why we usually draw field line diagrams in only 2 dimensions    R44
      • limitations of the 2-dimensional field line diagram    R44
    • 3.13 Interpreting field line diagrams    R44,45
      • an example using a pair of point charges    R44,45
      • description of the field line diagram    R44
      • analysis of the field line diagram    R44,45
      • actual charge distribution used in this example    R45
    • 3.14 Reasoning with field line diagrams    R45
      • 3 conclusions that can be reached through reasoning    R45
        • - Field lines do not cross each other    R45
        • - Field lines are not the paths of objects    R45
        • - The field is not strongest near field lines    R45
  • 4. REASONING AND SOLVING PROBLEMS USING PHYSICAL LAWS    R46-53
    • a list of the useful concepts, principles, and models presented so far    R46
    • 4.1. Reasoning with Newton's laws    R46-48
      • how this part of the Reader will be different from earlier parts involving forces    R46
      • an example involving Newton's 2nd and 3rd laws, as well as momentum conservation    R47
      • an example involving our model of materials    R47
      • an example showing how diagrams can be useful    R48
    • 4.2. Solving problems using Newton's laws    R48,49
      • an example involving the magnetic interaction    R48,49
    • 4.3. Reasoning with energy ideas    R49-51
      • table showing the major energy principles, with related concepts and their definitions    R49
      • an example involving the Work-Energy Theorem    R50
      • an example involving the Work-Kinetic Energy Theorem    R50
    • 4.4. Solving problems using energy ideas    R51-53
      • the procedure for determining potential energy    R51
      • some common reference points    R51
      • finding the potential energy stored in the field of two point charges    R51
      • choosing the reference point for two point charges    R51
      • mathematical expression for the potential energy for two point charges    R51
      • mathematical expression for the potential energy for two point masses    R52
      • an example showing how to apply gravitational and electric potential energy    R52,53
      • 5 common steps needed to solve problems using energy ideas    R53