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Fundamentals of Physics

PH 101 is one third of a Conceptual Survey of Physics

PH 101 Class Packet

Fall 2012

Outlines and Detailed Review Questions

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Physics 101

Students, Here is a detailed (and pretty complete) listing of review questions and chapter outlines covering the major and minor concepts from the class experience, including text, lectures, discussions, assignments, and activities. Use the questions:

to refresh your memory

to check how well you read the text and get understanding from the class

to prepare for class

to prepare for asking questions

to pinpoint areas of your knowledge needing more work

to keep track of your progress in learning the subject

to support your learning with others

to organize your notes

to organize your understanding Student experience has shown that these questions can be very helpful. Keep up with answering them to avoid getting overwhelmed by too many. Use them one chapter at a time, as we go over the subjects in class. Some people have found these questions more useful than doing exercises at the end of the chapters. You, therefore, may do the review questions as a substitute for the exercises, if you'd like. Use these review questions by yourself or with others. Let your instructor know how useful they are to you, and how you think they could be improved. There is some space at the end for you to record your comments throughout the term. Dennis Gilbert PH 101,2,3 Curriculum Coordinator

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DETAILED REVIEW QUESTIONS PH 101

Outlines and supplementary review questions for PH 101, Lane Community College, organized in line with the text (Conceptual Physics, 10th edition, Paul Hewitt) and our lectures/activities/labs.

TABLE OF CONTENTS

To Students . . . 1

Science, Physics, and the Newtonian Explanation and Description of Motion Chapter 1: About Science . . . 3,4 (Outline, Questions) Chapter 2: Newton’s First Law of Motion – Inertia . . 6,7 Chapter 3: Linear (Non-Rotational) Motion . . . 11,12 Chapter 4: Newton’s Second Law of Motion . . . 16,17 Chapter 5: Newton’s Third Law of Motion . . . 19,20

Momentum and Energy Explanations of Motion, and Rotation Chapter 6: Momentum . . . 22,23 Chapter 7: Energy . . . 25,26 Chapter 8: Rotational Motion . . . 30,31

Gravity and Motion in Gravity, and the Atomic Nature and States of Matter Chapter 9: Gravity . . . 37,38 Chapter 10: Projectile and Satellite Motion. . . 44,45 Chapter 11: The Atomic Nature of Matter. . . 48,49 Chapter 12: Solids . . . 51,52

More States of Matter (subject to time constraints) Chapter 13: Liquids. . . 57,58 Chapter 14: Gases and Plasmas. . . 61,63

Comments and Suggestions . . . 67 © copyright 1987-2012 Dennis Gilbert Do not copy without permission.

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1. About Science: Brief Overview

NOTE: The course will not cover Chapter 1 in the textbook, though it is interesting reading. Instead we will discuss the nature of science and the historical context of physics. The Nature of Science and Physics (Introductory comments)

Focus on Western Civilization to trace continuity to birth of modern science The lack of a category of science in some cultures, cultural prerequisites to

science The need for a discussion of some sophistication The nature of the birth of science as a major event

Science, Historically (in Western Civilization)

Historical distinctions and relations to other categories of knowledge Current categories within science, and currently changing categories

Physics, Historically

Historical distinctions and relations to other categories of knowledge Definition: Currently, What is Physics? Current categories within physics, and currently changing categories

What is Science? Developing sufficient understanding to enter the discussion and debate

Science as a process rather than a body of knowledge Science as a relation of concepts and experience

the relation in science the scientific spirit

Dogmatism as the opposite of science Exercise using the framework of science and dogmatism

A collection of other Questions and Contrasts

The question of a universal scientific method Science and mathematics Science and Religion/Mythology Science and technology Science and wisdom Objectivity and detachment and neutrality Science and the arts Science in the long historical perspective

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Chapter 1: About Science

Important Note: Chapter 1 of the text is interesting, and has much that pertains to our discussion. However, the text discussion is not nearly adequate for our purposes. The nature of science and physics as discussed in Chapter 1 and in class will deal with questions for which our class discussion is only an introduction. Full discussion is beyond the bounds of the course. Unlike the specific questions listed for other chapters, the questions below are mainly presented as a reminder of issues identified or discussed during class.

1. What is science: a body of knowledge or a human activity?

2. Is scientific knowledge the same as all knowledge?

3. Is there a general scientific method?

4. Is there a scientific method for physics?

5. What is a scientific attitude or spirit?

6. Science is centered in what general relationship?

7. What determines whether concepts are accepted and rejected in science?

8. What is the opposite of science?

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9. What is the relationship between science and technology?

10. What is the relationship between science and art?

11. What is the relationship between science and religion?

12. What is physics?

13. What are the branches of physics today?

14. Historically, how did science originate and evolve as a set of disciplines?

15. Historically, how did physics originate and evolve as a discipline?

16. If there is a major human evolutionary leap involving the recent tremendous advance of science, what might that leap be? What are some possibilities?

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2. Newton’s 1st

Law of Motion - Inertia: Brief Overview

Two Key Questions (to start with):

- Why do objects fall? - Why do thrown objects keep moving?

Aristotle's View and Its Decline

Motion due to its nature - the four elements and their relation to the center of the universe - the heavens and naturally "perfect" spherical motion

Motion due to a mover - the necessity of motion through a medium

Contrary observations, failed Aristotelian defenses, and the new views

- observation of moons of Jupiter, sunspots, stars, etc. - why objects should be expected to travel in straight level paths by themselves without a mover (Galileo's double inclined plane argument)

Galileo's contribution as key figure in birth of modern science

- years of persistent and brilliant work, though some ideas wrong (tides), others partially correct (impetus theory of motion) - description of mechanical motion (kinetics)

General Perspective

A theory of motion; an explanation of motion distinguished from its description Historical context of Newton, Newton's theories

Newton's First Law

Related terms, definitions, and distinctions - force, inertia, mass, weight (weight is discussed now because it is often confused with mass)

Vector and scalar quantities Examples and explanations using the 1st Law

Describing Situations of Zero Net Force Contact forces Tension and compression Mechanical and static equilibrium (a necessary, but not sufficient, condition) Galilean Relativity

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Chapter 2: Newton’s 1st

Law of Motion - Inertia

1. What was the Aristotelian view of why a rock would fall to the ground, and why a

heavy rock would (supposedly) fall faster than a light one?

2. What was the Aristotelian view of why an object, when thrown, would begin to move and why it would continue to move after it left the hand of the person throwing it?

3. Why specifically did people have difficulty accepting the following ideas and observations: objects fell at the same rate, there was a vacuum beyond the atmosphere, the earth moved, the Earth revolved about the Sun, there were Sun spots, other planets were round, Jupiter had moons, and the stars were very far away (since we didn't see them move as we moved around the Sun).

4. What was Galileo's argument for why it was reasonable to expect objects once set in motion to continue their motion in a straight line? (Consider his inclined plane experiments)

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5. What is inertia?

6. What are some phrases used to describe inertia? In what ways are they helpful, and in what ways are they misleading?

7. Galileo, most historians of science believe, did not have a mature concept of inertia, but had an impetus theory of motion to explain why objects could continue moving without an outside mover. What is an impetus theory of motion?

8. What was fundamentally important to Aristotle's description of motion, but which had no importance, or even meaning, for Galileo and later Newton?

9. What is the difference between a vector quantity and a scalar quantity? And what kind of quantities are mass and force?

10. What is Newton's First Law?

11. What is mass a measure of?

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12. What is weight, and how is it different from mass (in definition and kind of quantity)?

13. What does it mean to say one quantity is proportional to another? Use mass and weight as an example.

14. What is the weight of a 1 kg rock on the Earth's surface?

15. What is the mass of a rock whose weight is 4.9 N on the Earth's surface?

16. What are some phenomena primarily illustrating Newton's First Law? (For example, pulling paper towels off a roll, tightening a hammer head by hitting the handle, etc.)

17. How could you tell which of two objects had the greater mass if the objects were "weightless" by being far from where gravity was acting?

18. What is the standard unit of mass?

19. What is the standard unit of weight?

20. What is your mass and weight in standard international units?

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21. How is mass different from volume (in definition and in an example)?

22. In what kind of path would planets move if suddenly there were no gravitational interaction with the sun?

23. What is mechanical equilibrium, and when is an object in mechanical

equilibrium? 24. What is static equilibrium, and when is an object in static equilibrium? 25. What is the net force on a 10 N object sitting on a table?

26. What is the principle of Galilean Relativity?

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3. Linear (Non-Rotational) Motion: Brief Overview

The Frame of Reference and the Description of Motion Relativity in choice of reference points - no center to the universe The role of time - Galileo’s inclined plane experiments Describing process in an “object” ontology - the “movie model” of space, time and motion - dealing with issues raised by Zeno Description of Mechanical Motion in One Dimension Observation: “linear” ≠ “one-dimensional”

In one dimension, can represent direction by + or - Position and distance (as a function of time); the x vs. t graph Velocity and acceleration

vector quantity (magnitude and direction at each time) average and instantaneous values the v vs. t and a vs. t graphs

The case of constant velocity x = vt + x0 the x vs. t, v vs. t, and a vs. t graphs (with constant velocity) The case of constant acceleration v = at + v0 x = (½)at

2 + v0t + x0

the x vs. t, v vs. t, and a vs. t graphs (with constant acceleration) Two-dimensional Motion

Consider each component of the motion in each dimension as one-dimensional motion Use independence of motion in different dimensions (note: not just horizontal and vertical dimensions, or even dimensions at right angle directions)

example: kinematics of multidimensional constant velocity motion The Light Cone and the Structure of Causality (time permitting) Definition Comments

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Chapter 3: Linear (Non-Rotational) Motion

1. Assuming there is no special single point in the universe to relate motion to, in

what way is Galilean Relativity useful for choosing a reference point for motion?

2. What did Galileo observe about the motion of objects on an inclined plane that shows that describing motion with respect to time gives simplicity to the description?

3. Generally, in Galileo’s and Newton’s perspective (using an “object ontology”), how is motion viewed? How is this view of motion like a movie?

4. When an object in motion passes through a point, how much time is the object at the point?

5. Which of the following are vectors, and which are scalars: position, distance, speed, velocity, acceleration?

6. When vectors are defined in only one dimension, how can the direction of vector quantities can be simply represented?

7. How, in words, is the speed of an object defined?

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8. What is constant speed?

9. What is velocity? What is the difference between speed and velocity?

10. What is meant by average speed and instantaneous speed, and in what way is instantaneous speed a limiting case of average speed?

11. What are the standard units for the magnitude of velocity?

12. What is the meaning of positive and negative velocity?

13. What is acceleration?

14. What are the standard units for the magnitude of acceleration?

15. What is meant by positive and negative acceleration?

16. If an object moves with constant velocity, what is the relation among the distance traveled, the velocity, and the time spent traveling?

17. An object moves with constant velocity: what can be said about its acceleration?

18. An object moves with constant speed: what can be said about its acceleration?

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19. If there is constant acceleration, what is the relation among the velocity at a particular time, the velocity at a starting time (t = 0), and the acceleration?

20. If there is constant acceleration, what is the relation among the distance traveled at a particular time, the velocity at the starting time (t = 0), and the acceleration?

21. What are the meanings of the graphs of one-dimensional motion of x vs. t, v vs. t, and a vs.t?

22. Sketch these (above three) graphs for an object at rest?

23. … For an object moving with constant velocity?

24. … The three x vs t graphs for objects moving with the same constant acceleration; starting at x=0, and with zero, positive, and negative velocities?

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25. Is the acceleration constant or changing for a rolling ball or freely sliding ball on an inclined plane?

26. What is the maximum acceleration possible for a freely sliding ball on an inclined plane on Earth (depending on the angle of the incline)?

27. What is the acceleration of objects in free fall (i.e. when air resistance can be neglected) at the Earth's surface?

28. What accounts for the fact that different objects fall in air with different accelerations?

29. Why is it fundamentally wrong to refer to motion in several dimensions, or motion along a curved trajectory, as “nonlinear” motion in contrast to “linear” motion?

30. What is the light cone of an object at a particular point at a particular time? Draw the diagram, and give an explanation. (covered as time permits)

31. What does an object’s light cone have to do with the cause-and-effect relations to other objects in its future and its past? (covered as time permits)

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4. Newton's 2nd

Law of Motion: Brief Overview

Newton's Second Law

The formula and terms, a = F/m - net force, a and F in same direction

A picture of an object in isolation Reversing the hierarchy of x,v,a of Galileo’s description of motion

Examples and explanations using the 2nd Law Friction sliding and static friction Mass and weight Free fall without air resistance

Free fall with air resistance - terminal velocity

Fluid drag Insights from the mathematics of the Second Law The form of the law Why Newton had to invent calculus

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Chapter 4: Newton's 2nd

Law of Motion

1. What is Newton's Second Law?

2. What, precisely, do "a", "F", and "m" refer to in Newton's Second Law?

3. What is the relation between the direction of "F" and the direction of "a"?

4. How is the net force, F, figured out? How is a vector sum different from ordinary addition?

5. What is the net force on a 10 N freely falling body: when it encounters 4 N of air resistance? When the body is going up? When the body is going down?

6. What is friction, and what causes it?

7. What is static friction (in contrast to sliding friction)?

8. What is the magnitude of the static friction force (in terms of the other forces on the object) when an object is not moving?

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9. Usually, which is larger: the maximum static friction or sliding friction?

10. How is the difference in the static friction and sliding friction forces important in some practical ways? Give an example.

11. How is Newton's Second Law applied to free fall when air resistance can be neglected?

12. How is Newton's Second Law applied to falling objects with air resistance?

13. What is an object's terminal velocity, and why is there a terminal velocity of an object falling in air?

14. Of two objects of the same size and shape, why does the heavier one fall faster in air? (Recall in a vacuum, they fall with the same acceleration.)

15. Which encounters the most air resistance when falling: a small feather, or a baseball?

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5. Newton’s 3rd

Law of Motion: Brief Overview Newton's Third Law

Interactions between objects as pairs of equal and opposite forces The force pairs involving contact forces Examples and explanations using the 3rd Law Limits to the Third Law (comments)

Newton’s Laws Together

Role of inertial frames (subtle point) - fictitious forces

Mechanical Theories of Motion (Briefly)

General characteristics of mechanical motion - frame of reference independent of objects - clear separation of objects and environment - active cause of change of motion is outside the object

Mechanical theories in perspective -in physics; in other disciplines

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Chapter 5: Newton’s 3rd

Law of Motion

1. What is Newton's Third Law?

2. What part(s) of Newton's Third Law can be missed when it is expressed as "For every action there is an equal and opposite reaction"?

3. When an object is at rest on a table, the force of gravity on the object is equal and opposite to the force of the table on the object. Is this an example of Newton’s 3

rd Law? Why or Why not?

4. What are examples of phenomena illustrating Newton's Third Law? (recoil from a gun, rocket propulsion, etc.) Be as specific as possible.

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5. What is the reaction force of the gravitational attraction of a freely falling object?

6. Why is the above reaction force hard to notice in ordinary situations?

7. Why is a tug-of-war not won by the person who pulls the hardest on the rope (assumed to have negligible mass)?

8. What are the three general characteristics of a mechanical theory of motion?

9. What are some examples of theories (in physics, in other fields), which are not mechanical in the above sense?

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6. Momentum: Brief Overview

Momentum

Definition - vector quantity - units - dependence on frame of reference - examples

Perspective on momentum - as amplification and extension of Newton's Laws, in the evolution of physics - connection with inertia as a constant of the motion - connection to Newton's Laws - as reflecting a symmetry of nature

Impulse

Definition - vector quantity - units - examples

Explains why momentum changes General conclusions from the impulse-momentum relation

- maximizing (minimizing) momentum changes from a particular amount of force - maximizing (minimizing) the force from a particular amount of momentum

Examples (from martial arts, safety factors, etc.) Conservation of Momentum

Conservation of a vector quantity General form of conservation laws and their use Collisions: sticking (inelastic); bouncing (elastic); ambiguity in normal conversation More examples (rockets, recoil, pressure, etc.)

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Chapter 6: Momentum

1. What does the momentum of an object depend on?

2. What is the mathematical expression for momentum?

3. What kind of quantity is momentum? What are its standard units?

4. What is the cause of a change in momentum?

5. What is an impulse? What does it depend on?

6. What is the mathematical expression for impulse?

7. What kind of quantity is impulse?

8. How does the equality of the change in momentum and the impulse (the impulse-momentum relation) help explain several common phenomena? (For example, "following through" in baseball and golf, dash board padding, breaking bricks with karate, "rolling with a punch", safety nets, etc.)

9. What does it mean that momentum is conserved?

10. What does momentum being a vector quantity have to do with the meaning of the conservation of momentum?

11. When is momentum conserved?

12. What symmetry in nature is associated with the conservation of momentum?

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13. How does the conservation of momentum help explain several common phenomena? (recoil or "kick" from a rifle, rocket propulsion, collisions, the motion of fragments from an explosion, etc.)

14. How are the following distinguished: elastic collisions, partially inelastic collisions, completely inelastic collisions?

15. What are some common examples of collisions that are elastic, partially inelastic, and completely inelastic?

16. What happens to the momentum of objects when they bounce off each other as compared to when objects stick together?

17. If objects going in different directions were to stick together, how would their predicted final direction be figured out?

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7. Energy: Brief Overview Perspective on Energy

Criticism of naive textbook separation of energy and matter Historical development after Newton's Laws A transforming quantity A conserved quantity with its corresponding symmetry of nature

Quantity of Energy

Scalar quantity Units Dependence on frame of reference (for both potential and kinetic) Power, and energy compared to power

Work-Energy Relation and Kinetic Energy

Analogous to impulse-momentum relation Work as the cause of energy changes

definition and consequences of that definition - when no motion - when force perpendicular to the motion

Work-energy relation derived from Newton's 2nd Law Kinetic energy

Potential Energy

Definition, when it is possible to define For objects subject to a constant gravitational force Other examples (mass on spring, pendulum, etc.)

Conservation of (Mechanical) Energy

Use of conservation of energy and its generalization beyond mechanical energy Illustrations of conservation of energy

- pendulum; satellite motion; collisions, escape velocities, etc. Caution concerning friction Sources of energy (comments) Machines

Use of work concept to explain various machines - lever; block and tackle; screw jack; bicycle gears; wheel; etc.

Efficiency Comparison of Momentum and Energy

Similarities - conserved quantities and related symmetries - dependence on mass and velocity - relation to frame of reference

Differences - vector vs. scalar - impulse vs. work as source of change - "wallop" vs. "damage"

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Chapter 7: Energy

1. What causes a change in an object's energy?

2. What is the mathematical expression for work?

3. In what two different general situations can no work be done on an object even though a force is applied to it? (Be general.)

4. What are some specific examples of the above two general kinds of situations where no work is done on an object?

5. What kind of a quantity is work?

6. What is the meaning of positive work as compared with negative work?

7. What are the units of work?

8. What is power?

9. What are some situations illustrating the difference between work and power?

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10. What are the units of power?

11. What is kinetic energy (in words, don't just paraphrase the formula)?

12. What is the mathematical expression of the (translational) kinetic energy of an object?

13. How does kinetic energy underlie part of the kind of energy called thermal energy?

14. What, in general, is potential energy?

15. What is the mathematical expression of the gravitational potential energy of an object in the approximately constant gravity at the surface of the Earth?

16. What kinds of quantities are kinetic and potential energy?

17. How does the equality of the work done on an object and its change in energy (the work - energy relation) help explain several common phenomena? (the slowing of objects by friction, throwing an object into the air, etc.)

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18. How does the idea of work done by friction help explain why a wheel is so efficient?

19. What does it mean that energy is conserved?

20. To what symmetry of nature does the conservation of energy correspond?

21. What does it mean that mechanical energy is conserved?

22. How does the conservation of mechanical energy help explain several common phenomena? (the orbits of satellites, the constant speed of satellites in circular orbits and the varying speed in elliptical orbits, the increasing speed of objects as they fall, the motion of a pendulum, etc.)

23. What is the escape velocity of an object, and how, in words, is it figured out?

24. How is conservation of energy used to help explain how several common machines work? (the lever, the block and tackle, the screw jack, etc.)

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25. How is the efficiency of a machine defined?

26. About how efficient are the best designed engines? How is the energy “lost”?

27. How do kinetic energy and momentum compare in terms of their mathematical definition, the kind quantities they are, and what causes a change in each?

28. How do kinetic energy and momentum compare in terms of their intuitive meaning?

29. What are some situations that illustrate the difference in meaning of these quantities?

30. Where do organisms on Earth get their energy for life?

31. What is the principle difference between plants and animals in this regard?

32. What does the food chain have to do with the efficiency of use of the sun's energy?

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8. Rotational Motion: Brief Overview

Rotation in General

Comparison to “linear” motion - examples - preview of quantities - correspondence to linear motion relations

Distinguishing "revolution" and "rotation" Definition and description of rotational properties

- axis of rotation - angular velocity; contrast of velocity and angular velocity - units, and the use of radians - pseudo-vector quantities (magnitude and direction, with respect to axis)

Description of Linear Motion when there is also Rotation

Position taken to be center of mass (CoM) - center of mass and center of gravity (CoG) - finding CoG

For CoM - same results for velocity, acceleration, linear momentum, linear kinetic

energy - cause of change in linear momentum = net external impulse

Rotational Motion (about CoM usually) Rotational inertia (moment of inertia)

- dependence on axis, shape, mass Torque = Cause of rotation

- torque definition - units, pseudo-vector quantity - examples, including why objects roll, torque and weight

Stability condition for balance problems, etc. - role of center of gravity

Case of constant rotation centripetal force centrifugal force (artificial gravity) Centrifugal force as an instance of a fictitious force Rotational Energy and Conservation of Energy

- examples Angular Momentum

Conserved quantity and associated symmetry of nature Explanations based on concept of conservation of angular momentum

- effects in sports, weather pattern, precession of gyroscope, etc. Spin (quantized intrinsic angular momentum) and limits to the classical view of rotation

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Chapter 8: Rotational Motion

1. How is the angular speed of a rigid object related to the speed of different points on the object? (Recall from chapter 3.) (Make a sketch to help your explanation.)

2. What is the difference in meaning (in common language usage) in the statements that "a body rotates" and "a body revolves"?

3. What is the fundamental frame of reference for rotation?

4. What is the cause of rotation and changes in rotation?

5. What is the property of an object that is a measure of the difficulty of changing its rotational velocity?

6. On what does a body's rotational inertia, or moment of inertia, depend?

7. What are some examples of objects of the same mass with different moments of inertia?

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8. How is the idea of moment of inertia used to help explain several common phenomena? (the use of a long pole to keep one's balance, the different periods of pendulums of different sizes, the different accelerations of rolling objects, etc.)

9. What is torque?

10. What kind of quantity is torque?

11. What are the units of torque?

12. How does the torque depend on the axis of rotation and the applied force? (What are the five steps in determining torque?)

13. What is the difference between a vector and a pseudovector?

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14. In what general situation is it possible for two forces applied at two places on an object not to result in a torque with respect to any axis?

15. How is the idea of torque used to understand the action of forces when no rotation takes place? (i.e. What must be true?)

16. What are some of the static equilibrium situations in which the idea of torque is used to explain why no rotation takes place even though forces are acting?

17. How does the idea of torque help explain why a lever works?

18. How does the idea of torque help explain why a round object rolls (or doesn't)?

19. How can weight and torque be different (Give an example.)?

20. What is so special about the motion of the point called the center of mass?

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21. What is the center of gravity? The center of mass?

22. In what common situation is the center of gravity the same as the center of mass?

23. In what situation is the center of mass not at the same place as the center of gravity?

24. How can the center of mass or center of gravity of an object on the Earth’s surface be determined?

25. What is an example illustrating that the center of mass of an object need not be inside the object?

26. What are some example situations illustrating that the center of mass of a person does not always remain in the same place?

27. What does the stability of an object resting on a surface have to do with the object's center of gravity?

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28. How does the connection between stability and the center of gravity help explain several common phenomena? (inability to get out of a chair without bending over, or to bend over and touch your toes while standing against a wall, etc.)

29. What is a centripetal force and in what situations is it found?

30. What is a centrifugal force and in what situations is it found?

31. What, in general, is a fictitious force?

32. How can gravity be simulated in a space station (make a sketch)?

33. What is angular momentum?

34. What kind of a quantity is angular momentum?

35. What are the units of angular momentum?

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36. What causes a change in the angular momentum of an object or system of objects?

37. What does it mean that angular momentum is conserved?

38. Under what conditions is angular momentum conserved?

39. What is the symmetry of nature corresponding to the conservation of angular momentum?

40. How is angular momentum related to linear momentum?

41. How does the idea of the conservation of angular momentum help explain several common phenomena? (the changing angular velocity of a figure skater, diver, or gymnast, the rotation of air masses around high and low pressures, that it is easier balancing on a bicycle once it is moving, etc.)

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9. Gravity: Brief Overview More Clarity on What is Meant by a Theory, Model, and Representation (comments) Emergence of the Classical Concept of Gravitational Force up to Newton

The Aristotelian viewpoint Challenge of the Copernican view of planetary orbits Tycho Brahe's remarkable observations of planetary motion

- a different approach and contribution than Galileo Kepler's conclusions: Kepler's three laws (covered now rather than Chapter 10) on

- elliptical orbits - equal areas in equal times - period-radius relation

Kepler's mistaken viewpoint of gravitational force in the direction of velocity Newton's Formulation of the Law of Gravitation

Newton's proper understanding of force in the direction of acceleration Inverse square law relation from Kepler's Laws Universality of gravitation Law of gravitation

- examples of use (including finding oil, space flight, black hole discovery, extra-solar planets) - illustration of other inverse square law behavior

Consequences of, and Explanations Based on, Newton's Law of Gravity

Weight and weightlessness - weight and the sensation of weight

Tides, effect of Sun and Moon - other factors - tidal effects in general; examples

Effects of other planets - perturbations; discovery of new planets

Long term history of the universe and the missing mass question (brief comments) More Ideas and Questions in the Context of the Evolving Understanding of Gravity

Pre-classical mechanics views of Aristotle Newton's view of the gravitational force The idea of a gravitational field comparison of the force at a distance and the force field concept; representation of the gravitational field by lines of force; the - gravitational field inside and outside the Earth

- inside and outside a spherical shell Einstein's view of gravitation as a geometrical warping of space-time (comments only); black holes, gravity waves Unification of gravity with other interactions in nature Comments on the Intellectual Contribution of Newton's Law of Gravity to classical mechanics, to gravitation theory, to science generally, to philosophy

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Chapter 9: Gravity

1. What are distinctions in these concepts: theory, model, representation?

2. How do the above distinctions come up in understanding gravity?

3. Tycho Brahe is credited with making detailed measurements of planetary motions over many years which formed the observational basis for the discovery of several simple laws regarding planetary motion. What were his observational tools, the accuracy of his measurements, and the time period of the measurements?

4. What three laws did Johannes Kepler discover using Brahe's data?

#1: What is the shape of the path of each planet? What is the relation of the path of a planet to the sun?

#2: In what way do planets speed up and slow down in their orbits?

#3: How are the orbits of planets around the same sun related to each other? What is the relation between the period of a planet's motion around the sun and its distance (semi-major axis) from the sun?

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5. Why did Newton know that some force had to be acting on the planets as they went around the sun?

6. What did Kepler think was the direction of the force on the planets?

7. Contrast Kepler’s and Newton’s views on the direction of the force on a planet.

8. Therefore, what did Newton conclude from Kepler's Second Law about the origin of the force on the planets?

9. What did Newton conclude from Kepler's Third Law about how the force on the planets varies with distance?

10. How can we say the moon is falling when it isn't getting any closer to the earth?

11. What made Newton put aside his theory about planetary forces, and why did he publish it only 15-20 years later?

12. Newton didn't discover gravity, but what did he discover about gravity?

13. What is Newton's law of gravitation (the formula)?

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14. How does the gravitational force between two objects depend on the distance between them? On the mass of each? (Say in words.)

15. What are some other phenomena described by inverse square laws? (thickness of paint sprayed from a point, sound and light intensity from a point, etc.) (Make a sketch.)

16. Besides gravity, what were viewed in the early-middle 20th Century as the three “other” "fundamental" forces of nature?

#1

#2

#3

17. How can gravity be considered both the dominant force in the universe and the weakest force?

18. How can you feel weightless and still have a gravitational force act on you?

19. How could you detect the difference between the apparent weightlessness of an astronaut in orbit around the earth and the real weightlessness of an astronaut far out in space, far from any attracting bodies?

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20. What about the gravitational force from the moon is responsible for tides?

21. Why is it that the water bulges on the side of the earth facing the moon and the opposite side too?

22. Why are there approximately two high tides each 24 hrs?

23. Why are there not exactly two high tides each 24 hrs?

24. Why is the sun less than half as effective as the moon in causing tides on the earth and yet the force of the sun on the earth is about 180 times stronger than the force of the moon on the earth?

25. How is it obvious that the sun exerts a greater force on the earth than the moon exerts on the earth?

26. What are some factors that make tides a complicated phenomena?

27. In what situations do the sun- and moon-caused tides coincide, and what are such tides called?

28. In what situations do the sun- and moon-caused tides moderate each other, and what are such tides called?

29. How big and how often are the high tides on the solid mass of the earth?

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30. What is probably the most important effect of atmospheric tides?

31. How does viewing gravity in terms of action at a distance compare with viewing it in terms of a gravitational field?

32. How is the gravitational field of the earth represented pictorially?

33. How does the gravitational field of the earth vary inside the earth, and what is the value of the field at the center of the earth? (Sketch a graph.)

34. Why does a spherical shell of matter produce a zero gravitational field inside it?

35. What is evidence that the gravitational force between two objects is not shielded by matter between?

36. In explaining what other phenomena is it useful to use the force field concept?

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37. How does Einstein's view of gravity compare with the view of it as a force or a

field existing in space?

38. Why is it appropriate to call some collapsed stars "black holes"?

39. How is the mass of a black hole related to the mass of the star that collapsed to form it?

40. What is the principal reason gravity is so intense near a black hole?

41. Why are the sun and the earth and other planets and moons spherical in shape?

42. Why are the sun, earth and other planets and their moons not exactly spherical?

43. Why are the forces of the planets on each other referred to as "perturbations" in relation to the force of the sun on the planets?

44. In general, how were the existence of Neptune and Pluto predicted?

45. How has the long term fate of the universe been seen to depend on its total mass?

46. What are some ways Newton’s law of gravity is used today?

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10. Projectile & Satellite Motion: Brief Overview Projectile Motion

Make judicious choice of coordinates (gravity acting along one and/or initial velocity along one) Kinematics in vertical and horizontal directions

- constant velocity in horizontal - constant acceleration in vertical

Examples (note independence of motion in different dimensions) (illustrated in "shoot the monkey" demonstration) Properties of projectile motion

- maximum range (at 45 degrees) - effect of air resistance examples

Satellite Motion

Like long projectile motion - misunderstandings (including “escaping gravity”, “not falling”)

Orbital Motion Considered as Falling Projectile Motion

Circular orbits orbital velocity; example (8 km/s at earth surface) geosynchronous orbits

Elliptical orbits ellipses, definition

Energy Conservation and Satellite Motion

Comparison of potential energy and kinetic energy at different points in the orbit Work done at different points in the orbit

Escape Speed For different bodies

- dependence on mass and distance example (11.2 km/s at earth surface) In complex systems using Jupiter to get out of the solar system

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Chapter 10: Projectile & Satellite Motion

1. When describing projectile motion, why is it convenient to look at each

component of its motion separately?

2. When describing projectile motion, why is it convenient to choose to look at the horizontal and vertical components?

3. What is the chief characteristic of the vertical component of projectile motion?

4. What is the chief characteristic of the horizontal component of projectile motion?

5. What is the shape of a projectile's trajectory?

6. What is the relation between the straight line path of a projectile if there were no gravity, and the actual trajectory with gravity?

7. How far below an initial straight line path will a projectile fall in 1 sec, 2 sec, 3 sec, etc.?

8. Does air resistance have much effect on projectiles that go long distances?

9. What do the vertical height and horizontal range of a projectile depend on (assuming no air resistance)?

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10. At what angle should a projectile be sent off to get the maximum range, or does the angle matter (assuming no air resistance)?

11. An angle too high will give less than the maximum range. What too low angle will give the same less than maximum range? (Assuming no air resistance)

12. Assuming no air resistance, what is the relation between the speed of a projectile leaving the ground and returning to the ground?

13. Assuming no air resistance, what is the relation between the velocity of a projectile leaving the ground and returning to the ground?

14. Assuming there IS air resistance, what is the relation between the speed of a projectile leaving the ground and returning to the ground?

15. Which way is it easiest to launch a satellite: East, West, North, or South? (Or does it matter?)

16. Why is it incorrect to say a satellite does not fall?

17. Why is it incorrect to say a satellite has escaped gravity?

18. What is meant by tangential velocity (as used in this chapter)?

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19. How fast does an object have to be going to travel in a circular orbit around the earth (close to the surface, but above most of the atmosphere)?

20. If an object is launched faster (than above), what kind of orbit will it have?

21. What exactly is an ellipse? Is the speed constant or changing for an object in a circular orbit? In an elliptical orbit?

22. How fast does a satellite have to go to escape from the Earth?

23. What would happen if a satellite were launched straight up? (How does the answer depend on the satellite's speed?)

24. What are the points of greatest and least kinetic energy and potential energy of a satellite in an elliptical orbit?

25. In what kind of orbit are the kinetic energy and the potential energy each constant?

26. How are objects able to escape the solar system, even thought they may start out at velocities less than their escape velocities?

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11. The Atomic Nature of Matter: Brief Overview

Context for Viewing the Atomic Nature of Matter

Existence of properties beyond motion in classical mechanics - beyond explanation in terms of "force'', "mass", ''space and time''

Two ideas originating in ancient times - That the properties of any substance come from the properties of a relatively small number of elements that make up that substance. - That the properties of each substance do or do not persist as the amount of the substance decreases.

The atomic idea fully accepted within science relatively recently rise of chemistry in 1800's evidence for atoms

- invariant proportions of substances in chemical reactions - successful theories based on atomicity - Brownian motion, and Einstein's theory of it - from advanced photographic techniques etc.

Thinking "atomically" in general examples

Atoms

Historical reference to atoms as "elements" Small size

comparisons molecules in breathe vs. breathes in atmosphere molecules in thimble of water vs. thimblefuls in oceans

can't be seen with visible light Numbers: 90 natural, 19 more artificial isotopes Molecules as specific combinations of atoms Compounds and mixtures Atomic and molecular masses

amu's and Avogadro's number Atomic structure

Nucleus, nucleons, electrons, relative scale in size and mass Chemical properties dependent primarily on outer electrons

shell structure, hence periodic table of elements Chemical potential energy

the concept examples

The Search Goes On:

In atoms: electrons, protons, neutrons The "standard model": quarks and leptons

3 families of each, so far matter and anti-matter quarks as a new kind of element (More in PH 103)

Dark matter, dark energy

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Chapter 11: The Atomic Nature of Matter

1. People within many ancient cultures believed that motion and other properties of

objects depended on their relative composition of a small number of elements, though there was not agreement on what those elements were. Even with similar views of elements, people held fundamentally different beliefs about the form of these elements. On what about the form did they not necessarily agree?

2. When was the atomic theory of matter first formulated on the basis of an extensive investigation of nature?

3. How many kinds of atoms are there?

4. How many different kinds of atoms can be found existing naturally on the earth, and how many must be artificially produced?

5. About how many elements compose most familiar things?

6. Living organisms are composed primarily of what four elements?

7. Atoms are so small, that in one breathe there are as many atoms as there are ... what?

8. Atoms are so small, that in 1 cm3 of ocean water there are as many atoms as

there are ... what?

9. Why can atoms not be seen directly with visible light?

10. What phenomenon was the first direct evidence of atoms (in 1827) and who developed the theory of this phenomenon many years later (in 1905)?

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11. What causes Brownian motion?

12. What other direct evidence of atoms exists today?

13. What distinguishes atoms from molecules?

14. What are some common examples of molecules?

15. What does the term "chemical reaction" refer to?

16. What is Avogadro’s principle?

17. What is an atomic mass unit?

18. How is the molecular mass (sometimes called “molecular weight” (sic)) of a substance determined; and once known, how is it used to determine the numbers of molecules in a known mass of a substance?

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19. What distinguishes compounds and mixtures from each other and from molecules?

20. How are mass and charge distributed in an atom?

21. What are the names, relative masses, and charges of the constituents of an atom?

22. What would the sizes of the parts of an atom be, assuming the atom itself were the size of the earth?

23. What determines the main characteristics of atoms?

24. What is the atomic number of an atom and why are atoms classified according to their atomic number?

25. What is the basis for lining up elements vertically in columns in the periodic table of elements?

26. What particles are the building blocks of nucleons and many other sub-atomic particles?

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27. What characteristic determines whether a particle is referred to as a hadron or a lepton?

28. How many families of quarks and leptons are presently thought to exist?

29. What is anti-matter?

30. When was anti-matter first observed to exist?

31. What is meant by a state of matter?

32. What are four commonly observed states of matter?

33. Which is thought to be the most common (currently directly observed) state of matter in the universe at this time?

34. On what variable does the state of a particular substance depend on most?

35. What is dark matter?

36. What is dark energy?

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12. Solids: Brief Overview

Context of Discussion of States of Matter

To this point: properties dependent on the elements Now: properties dependent on the state of organization of the elements

- solid state - liquid state - gas state - plasma state - others

What else: properties dependent on the change of state of organization Subtle point: What we choose as elements is not separate from their state of organization Technology on the horizon: materials construction on the atomic level

The Solid State

General definition of a solid crystalline solids amorphous solids

Evidence for this picture of the solid state x-ray diffraction theoretical predictions

(Atomic) Bonding of Solids

Ionic, Covalent, Metallic, Van der Waals bonding (comments only)

Elementary Characteristics of Solids

Density: relating mass and volume Elasticity: relating forces and distortion Tension and compression

- why an I-beam works - why arches work

Scaling, A Useful, Insightful Concept

Properties dependent on length, area, volume Relative scaling of length, area and volume Consequent scaling of those different properties Also, dependence on shape Examples of phenomena and explanations based on scaling

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Chapter 12: Solids

1. What is the difference in microscopic structure between a solid and a liquid or a gas?

2. What is a crystalline solid? An amorphous solid?

3. What was the first direct evidence that many solids are crystals (in their microscopic structure)?

4. What are the four principal types of atomic bonding in solids?

#1 #2

#3 #4

5. What is the basis for the difference in properties of graphite and diamond?

6. What does density refer to?

7. Distinguish density, mass, and volume.

8. Why is the density of a lake of water the same as a cup of water?

9. What is the main basis for the difference in density of different elements in their solid state?

10. What is elasticity?

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11. How is the force applied to a spring related to the amount of elongation?

12. Why is an I-beam a good design for beams?

13. Why is an arch a good design for stone roof structures?

14. How do the size, area, and volume of an object scale?

15. How, in general, does the concept of scaling explain many phenomena?

16. What are several specific examples of scaling explanations of phenomena?

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13. Liquids: Brief Overview

Distinguishing the Liquid from Solid State

Microscopically in terms of movement in terms of order

Macroscopically in terms of ability to support a shearing stress (thus) in terms of ability to flow, conform to container

Pressure

Definition units (Pascals, atmospheres) examples (pressure =/ force)

Pressure in Liquids

Dependence on depth alone, and not volume or direction examples

Transmission of pressure Pascal's principle more examples (including the Cartesian diver)

Buoyancy

Definition Reason for buoyant force Dependence of buoyant force on object and fluid

Archimedes' principle statement of reason for examples

Sinking and floating examples

Surface Tension

Definition Reason for surface tension Examples

Capillarity

Definition adhesion and cohesion

Reason for capillarity Examples

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Chapter 13: Liquids

1. At a microscopic level, what distinguishes a liquid from a solid?

2. At a macroscopic level, what distinguishes a liquid from a solid?

3. What is pressure?

4. What are some situations that illustrate the difference between pressure and force?

5. What causes the pressure in a liquid?

6. At any point in a liquid, how is the pressure in one direction related to the pressure in another direction?

7. How does the pressure at a point in a liquid depend on the weight density of the liquid and the depth of the liquid at that point?

8. What are some things that pressure in a liquid does not depend on?

9. What is the underlying reason that "water seeks its own level"?

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10. What are the units of pressure?

11. What is buoyancy?

12. Why is there a buoyant force?

13. What is the magnitude and direction of the buoyant force?

14. In an incompressible liquid, how does the buoyant force depend on depth?

15. How does the buoyant force depend on the weight of the object?

16. What determines whether an object will sink or float (neglect surface tension)?

17. What is Archimedes' Principle, and how does it help explain several phenomena? (that a metal boat can float, the submerging and surfacing of submarines, objects floating higher in salt water, etc.)

18. What determines the level a floating object will float in water?

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19. What is a "Cartesian diver" and how does it work?

20. When iron in a boat is thrown out into the pond in which the boat is floating, what happens to the water level of the pond? Why?

21. If pressure is increased in one part of an enclosed fluid, what happens in the rest of the fluid?

22. What is Pascal's Principle?

23. How does a hydraulic press work? (both in terms of pressure and in terms of work) (make a sketch)

24. What is surface tension?

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25. How is the idea of surface tension used to help explain several common phenomena? (the shape of liquid drops and soap bubbles, the spreading of one liquid on another, the formation of drops of one liquid on another, cold soup tasting greasy, insects' ability to walk on water, etc.)

26. What is capillarity?

27. What is the cause of capillarity?

28. What distinguishes adhesion from cohesion?

29. How is the idea of capillary action used to help explain several common phenomena? (paint or water rising up a paint brush, steel wool holding liquid, water traveling sideways and up through soil, etc.)

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14. Gases and Plasmas: Brief Overview

Gases

Perspective on this state as fluids difference from liquids

Our Atmosphere

The Earth as container Atmospheric pressure

the discovery and explanation (from early 1600's) von Gueircke's hemispheres Torricelli's barometers Boyle's Law (and its historical origin)

explanations based on air pressure, examples The buoyancy (and density) of air

examples Bernoulli's Principle

Statement of Reasons for

conservation of energy Examples

Plasmas

Perspective on this state as a fluid difference from other fluids common occurrence

Examples

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Chapter 14: Gases and Plasmas

1. At a microscopic level, what distinguishes a gas from a liquid?

2. At a macroscopic level, what distinguishes a gas from a liquid?

3. Why are gases and liquids referred to as fluids?

4. What two factors account for the Earth keeping its atmosphere?

5. How high above sea level is the boundary between the top and bottom halves (by mass) of our atmosphere?

6. Why does the atmosphere exert pressure?

7. How is the idea of atmospheric pressure used to help explain several common phenomena? (the difficulty in pulling apart a container with a vacuum inside, drinking with a straw, the working of a barometer, etc.)

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8. Why can water be pumped up only about 10.3 m (or 33 ft) when the pump is at the top of the column of water?

9. What is the mass of 1m3 of air? What is its weight?

10. About how high can atmospheric pressure at the Earth's surface lift a column of mercury?

11. What is the relationship between the pressure and volume of a particular amount of gas, assuming the temperature remains constant?

12. What is Boyle's Law, and how is it used to explain several common phenomena? (our ability to pump tires up to pressures higher than atmospheric pressure, why rapidly ascending divers must exhale continuously, etc.)

13. When can a gas be accurately considered as an "ideal gas"?

14. What is the magnitude and direction of the buoyant force of air on an object?

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15. How do hot air balloons work? (Make a sketch)

16. Why do helium balloons rise?

17. Why will a helium balloon only rise so far? (Make a sketch)

18. What determines how high it will rise?

19. How is the pressure of a fluid related to its velocity?

20. What, in words, is Bernoulli's Principle?

21. Why, from the point of view of energy conservation, is it reasonable to suppose pressure will decrease with increasing fluid velocity?

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22. What are several common phenomena that are explained through the use of Bernoulli's Principle? (puffing out of a convertible top while driving, curve balls, sailing boats, etc.)

23. At the microscopic level, what distinguishes a plasma from a gas?

24. At the macroscopic level, what distinguishes a plasma from a gas?

25. What are some everyday examples of matter in the plasma state?

26. How do the properties of plasmas account for several common phenomena? (magnetic storms influencing the Northern Lights, differences in TV and AM radio transmission over long distances, power production using plasmas, etc.)

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Comments and Suggestions

Please write down your thoughts on the value of these chapter outlines and review questions as you use them throughout the term. Also, record and share any suggestions you have for making them more helpful. Thanks.