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PHY 115 Learning Goals Outline October 2011 Unit 1: Energy and Power 1. Define and list the units for: a) heat b) energy c) mass d) power How is energy related to heat? What is energy? What is power? How do they differ? What are the units used to describe both? What is mass and what are its units? How may kg is 100 lbs? 2. Include units with physical quantities, and ask for units if none are given 3. Convert between basic units What are the relations between Calories, joules, kilojoules? 4. Relate physical quantities to common experience 5. Estimate physical quantities (what numbers are or aren't reasonable answers to a problem) 6. Distinguish ideas grounded in scientific models from those that are not 7. Identify explosions as examples of energy transformations What is an explosion? Why is the difference between an explosion on Earth and an explosion in space? 8. Compare substances quantitatively using the measure of energy per unit mass Energy game: How does the energy per gram of TNT compare to a cookie, compare to uranium, etc.? What forms of energy do each have? 9. Observe that an object's appearance does not reveal how much energy it contains. Energy game. What forms of energy does each energy source have? 10. Relate quantitative differences in energy concentration to political and economic events 11. Apply proportional reasoning to the dependence of kinetic energy on the square of velocity What do bullets and asteroids have in common? Why are their energies so different? 12. Quantitatively and qualitatively compare the kinetic energies of common objects 13. Analyze equations to determine when physical quantities are more sensitive to changes in one variable compared to another Is kinetic energy more sensitive to changes in speed or changes in mass? 14. State the principle of conservation of energy 15. Distinguish something that is energetic from something that is powerful 16. Identify when you would want something that is energetic, versus something powerful, versus both What do TNT and cookies have in common? What is different? How does this affect their use? 17. Distinguish between power used and useful power Is it possible for a 25 W lightbulb to be as bright as a 100 W lightbulb? If not, why not? If so, how? 18. Recognize the cost of making and transporting energy sources 19. Evaluate trade-offs between different sources of energy Why is hydrogen a potential fuel? How does it work? Why is this an example where it costs energy to make energy? Why aren’t we using hydrogen instead of gasoline already? When the Sun is shining, how much solar energy falls on a square meter of the Earth each second? Why do we express this in terms of power? Is this energy usable? Practical? Unit 2: Atoms & Heat 20. Define and list the units (and convert among common units) for: a) Temperature b) Specific heat How is heat related to temperature? What is specific heat and what does it depend on? 21. Know the 0th Law of Thermodynamics (equilibrium) 22. Explain the difference between heat and temperature 23. Relate heat energy to the kinetic energy of atoms and molecules How is temperature related to the physical properties of atoms: How does it depend on their mass and speed? 24. Apply proportional reasoning and the equation for specific heat to quantitatively relate heat energy and temperature 25. Compare the specific heats of different materials and interpret the meaning of the differences Is the specific heat of water greater or less than aluminum, and what does that information tell us? 26. Relate quantitative differences in specific heats to common experiences and realworld applications 27. Apply heat conduction to explain why different materials at the same temperature feel like they have different temperatures Why do a plastic and glass cup at the same temperature feel as if they are at different temperatures when you touch them? 28. Know the 1st Law of Thermodynamics (energy is conserved) 29. Apply the 1st Law of Thermodynamics to predict the final temperature of a mixture of liquids, given the initial amounts and temperatures of the liquids If you mix two cups of water at different temperatures, what temperature will they reach over time? How does it depend on the temperature and volume of water in the two cups? 30. Know the approximate speed of sound, and that this equals the typical velocity of molecules What is the typical speed of atoms and molecules in materials? 31. Relate the quantitative difference between the speed of light and the speed of sound to common experience How is the typical speed of atoms and molecules related to lightning? 32. Estimate the heat energy in ordinary objects; quantitatively compare an object's kinetic energy to its heat energy How does the kinetic energy of a fastball (when thrown by a pitcher) compare to its heat energy after it is caught? Be quantitative. 33. Estimate the final temperature of an object moving through the atmosphere if all of its kinetic energy is converted into heat energy (through friction) How does an asteroid cause an explosion? 34. Explain how an asteroid could end up hotter than the sun before hitting Earth 35. List and describe evidence that supports the model that things are made from atoms 36. Apply the atomic model to explain thermal expansion When the temperature of a bar of steel is increased by one degree, what happens to its length? Compare to what happens if you increase the temperature of a balloon filled with air. Compare to what happens when you increase ice one degree above the melting temperature and it becomes liquid water. Explain why ice contracts when heated 37. Give examples of thermal expansion in common experience 38. Apply expansion due to heating to explain how global warming causes the oceans to rise 39. Apply the atomic model to explain the relationship between temperature and pressure How is pressure related to temperature in a gas? 40. Apply the relationship between temperature and pressure to common experience How is this related to explosions? 41. Describe entropy. Describe an example of increasing entropy (no need to demonstrate) 42. Describe the 2nd Law of Thermodynamics 43. Explain why converting heat energy to kinetic energy is much harder than converting kinetic energy to heat energy Which is easier: converting kinetic energy to heat or converting heat to kinetic energy? Or is it equally easy? What laws of thermodynamics apply? What has this to do with order and disorder? 44. Apply the definition of efficiency to quantitatively compare power used and useful power Unit 3: Force and Gravity 45. Define and list the units (and convert among common units) for: a) Force b) Acceleration c) Momentum d) Velocity 46. Distinguish between velocity and acceleration 47. Identify and describe Newton's three laws of motion 48. Determine whether there is a net force on an object based on a description of the object's motion If an object travels at a constant velocity (zero acceleration), what can you conclude about the NET force on the object? If you are driving a car in a straight line at constant speed, what is the net force on your car? Given you answer, why do you need to use your engine at all? 49. Describe and predict the motion of an object subject to a net force What is the relation between the direction of the force and the direction of the acceleration? the direction of the velocity? 50. Apply Newton's 3rd Law (action-reaction) to real-world situations What does the law of action-reaction mean? Why don’t forces always cancel because of it? 51. Explain how Newton's 3rd Law relates to conservation of momentum 52. Know how the momentum of a system depends on its mass and velocity 53. Give examples of the quantitative predictive power of Newton's laws 54. Identify limitations of the predictions of Newton's laws 55. Know the equation for the universal law of gravity, and the units for the gravitational constant 56. Explain the physical meaning of the universal law of gravity (as an interaction), and why it is called universal What is the direction of the gravitational force of one object on another? 57. Define weight and know the equation for the (approximate) weight of objects near the Earth's surface 58. Distinguish between "feeling weightless" and "having no weight" How weightless is an astronaut orbiting 200 km above the surface of the Earth? Explain your answer. 59. Describe how a force parallel to the velocity of an object affects its motion 60. Describe how a force perpendicular to the velocity of an object affects its motion 61. Explain why an object moving in a circle at a constant speed must have a force acting on it, and identify the direction the net force on it 62. Describe how the acceleration of an object moving in a circle with a constant speed (uniform circular motion) depends on the speed of the object and the radius of the circle 63. Apply uniform circular motion and the law to gravity to explain how the period of a satellite's orbit depends on the radius of the orbit Why do geosynchronous satellites have to be far from the Earth? About how long do low Earth orbit satellites take to orbit the Earth? 64. Explain why the period of certain satellites is important 65. Know the speed required to orbit the Earth near the Earth's surface 66. Know the equation for gravitational potential energy, and the approximate equation near the Earth's surface 67. Apply energy transformations to relate changes in height to changes of speed of an object freely moving under the influence of gravity As you begin to go down a frictionless slide, you drop an apple over the side. Which reaches the ground first, you or the apple? Which has the greatest velocity? Explain. 68. Know the speed needed to escape the Earth's gravity, and explain how to find it using conservation of energy How does escape velocity depend on the mass and radius of the planet? 69. Define air resistance and describe how it depends on the density of air, the shape of the object, and the speed of the object 70. Define terminal velocity and explain how to calculate it using Newton's laws How do you compute terminal velocity (how do you derive it)? What does the terminal velocity depend on? 71. Calculate the energy supplied by an engine to overcome air resistance in terms of the force of air resistance and the distance traveled 72. Explain how air resistance affects gasoline consumption Use this explain whether it costs more gas to travel 30 mph or 60 mph if you want to travel from Princeton to New York City. 73. Apply conservation laws to make quantitative predictions What is conservation of energy? Conservation of momentum? Find an example where conservation of energy is the easiest (only?) way to solve a problem. Find an example where conservation of momentum is the only way to solve a problem. If a bomb explodes and breaks into two pieces of shrapnel in which one is twice the mass of the other, what can you say about the directions the two pieces travel? Their speeds? Their kinetic energies? When is a system's energy or momentum not conserved? 74. Define and distinguish antimatter, dark energy, and dark matter What is the mass and charge of an antiproton (compared to a proton)? 75. Explain what distinguishes chaotic motions, and give real-world examples where chaos theory is important How is it that “they can send a man to the moon but they cannot predict the weather”? 76. Apply proportional reasoning to all of the quantitative physical relationships above (how one quantity scales with another quantity) How does kinetic energy change if you double the mass? The speed? Same questions for momentum. Unit 4: Radioactivity 77. Define radioactivity 78. Know approximately how much energy (in calories) is released in the radioactive decay of a single nucleus 79. Know the absolute and relative sizes of an atomic nucleus and an atom 80. Identify the particles that make up an atom 81. Describe the structure of an atom 82. Define atomic number and atomic mass in terms of the constituents of atomic nuclei What does atomic weight tell us about the nucleus? What does atomic number tell us? What is an isotope? If two atoms have nuclei that are different isotopes of the same element, how does this affect their chemical properties? Nuclear properties? 83. Describe what happens to an atom during nuclear fission A nucleus decays into fission products and light mass (or zero mass) particles. What are the possible light mass particles (should be able to name five and know their charges)? 84. Define alpha, beta, and gamma rays 85. Apply conservation laws to explain why alpha, beta, and gamma rays are more dangerous than the heavier nuclei that produce them In radioactive decay, which is more dangerous, the fission products or the light mass (or zero mass) particles? Be prepared to explain why using the conservation of momentum and energy. 86. Rank alpha, beta, and gamma rays according to penetrating power Which type of ray is easiest to stop? Which is hardest to stop? 87. Apply conservation of nucleons and conservation of charge to nuclear reactions To have a radioactive decay, what condition(s) have to be satisfied about the nucleus that decays and the nuclei and rays that are produced from the decay? 88. Explain how we know that mass is not always conserved ("conservation of mass" is a law that has been disproven) What is the equation E=mc2 telling us about mass and energy? Why does a block of uranium have so much more energy than a fastball? What form of energy is it? (nuclear energy is not good enough: I mean microscopically, what kind of energy is being converted into heat?) 89. Give examples of real-world applications of radioactivity If someone drinks gin, why is it important that it be radioactive? 90. Describe a chain reaction. 91. Define half-life. Given the half-life of a radioactive substance and an initial amount, estimate how much will remain after a given interval of time. 92. Define exponential growth, and give examples Unit 5: Waves 93. Define and list the units (and convert among common units) for: a) frequency b) period c) amplitude d) wavelength 94. Describe what a wave is, and its amplitude, frequency, and wavelength. 95. Compare the transport of mass for a projectile to the transport of energy for a wave. How can waves be used to send information? 96. Distinguish between transverse and longitudinal waves, and identify waves which are neither. 97. Identify what factors do and don’t affect the speed of a wave (and under what conditions). 98. Know and apply the mathematical relationship between speed, frequency, and wavelength of a wave. Is the relation the same for all kinds of waves? 99. Draw a snapshot graph of a continuous wave if you know its amplitude, wavelength, and speed. 100. Describe how a wave propagates through a medium. 101. Explain the importance of the "springiness" of the medium in wave propagation. 102. Describe wave reflection and give examples. 103. Define dispersion and describe what it means for a medium to be dispersive. If a medium is dispersive, what does that say about the speed of waves in it? Compare dispersion in deep water waves versus shallow water waves. 104. Describe refraction and give examples. 105. Explain what causes a wave to refract. 106. Describe wave interference, and give examples. What is the interference pattern when a plane wave hits a wall with two slits? How does it depend on the separation between slits? 107. Distinguish between constructive and destructive interference. 108. Illustrate wave interference using "movie pictures" (history plots) of waves. 109. Distinguish between intensity and amplitude of a wave. 110. Describe how a "standing wave" is created. 111. Describe diffraction, and give examples of diffraction (for both sound waves and light waves). 112. Describe resonance, and what causes something to resonate. 113. Explain how you can combine sounds to make a beat frequency. 114. Apply a qualitative understanding of the above phenomena (reflection, refraction, dispersion, interference, diffraction, resonance, beats) to explain observations in your daily life. How does speed of shallow wave vary with depth? How is this related to tsunamis? Why can you hear people across a lake at night, but not during the day? 115. Qualitatively describe what an electric field is, and identify what causes or creates an electric field. 116. Describe the Coulomb force law between two electric charges. Know how the force depends on the magnitude of the charges and the distance between them. 117. Qualitatively describe what a magnetic field is, and identify what causes or creates a magnetic field. 118. Qualitatively describe effects of electric and magnetic fields on electric charges and currents. 119. Describe an electromagnetic wave: how the direction of propagation compares to the directions of the magnetic and electric fields, and how such a wave may be produced by an oscillating electric charge. Sketch the pattern of electric and magnetic fields. What happens to electric and magnetic fields if you move a charge? if you move a magnet? how is this related to electromagnetic waves? 120. Describe and identify parts of the electromagnetic spectrum Be able to order from highest to lowest frequency: radio waves, microwaves, infrared, visible, ultraviolet, x-rays, gamma rays 121. Given a certain frequency of electromagnetic radiation, estimate the physical size of a detector that would detect it. Unit 6: Quantum Physics 122. Identify experimental results that led to the quantum revolution. 123. Identify and describe five surprising observations that only are explained by quantum physics. 124. Identify four devices or technologies that affect your daily life and that were invented thanks to our understanding of quantum physics. 125. Define a quantum. 126. Describe Planck's Law. 127. Apply Plank's law to rank the energies of different kinds of photons (e.g. radio waves, visible light, x-rays). Which has greater energy, a quantum of x-rays or a quantum of radio waves? 128. When a metal is heated in a flame, describe how the color of the metal depends on the temperature. 129. Sketch a qualitatively correct graph of intensity vs. frequency of light emitted from a mental rod held in a flame. Describe how this plot contradicts the predictions of classical physics, and how quantum physics resolved the contradiction. 130. Describe the photoelectric effect. Describe how the effect differs from the expected results from classical physics. Describe how quantum physics explains the actual experimental observations. How does the number of electrons ejected depend on color? on intensity? 131. Describe the spectrum of light emitted from hot hydrogen gas. 132. Explain how atomic spectra provide observational evidence for quantum theory. Why does hot hydrogen gas only emit certain discrete colors (spectral lines)? 133. Explain how the spectrum emitted by hydrogen provides information about the energy levels of electrons in hydrogen gas. 134. Explain how atomic spectra may be used to determine the composition of stars. 135. Describe the Bohr model of the atom, including his formula for energy levels. 136. Explain why, according to classical physics, atoms should not exist. 137. Describe wave-particle duality and give examples (how has it been observed). What happens when you fire single photons through a narrowly spaced pair of slits? what does this tell you about photons? How does the pattern change if I close one slit? If I have both slits open but use a detector to determine which slit the electron goes through? How is the pattern different if I use electrons instead? 138. Describe the Heisenberg uncertainty principle. Describe how you might "see" this principle if Planck's constant were much larger. How is it related to the problem with Rutherford’s model of the atom? 139. Describe how quantum uncertainty is different from classical measurement uncertainty. What does quantum physics says about determinism? What is the role of “waves” in quantum theory? Unit 7: Special Relativity 140. Know that Maxwell's equations imply that the speed of light is constant. 141. Using an example with two observers moving relative to each other, explain how Newton's ideas of time and space are inconsistent with the idea that the speed of light is constant. 142. Describe an "inertial reference frame". 143. Describe what "time dilation" means. 144. Explain how the constancy of the speed of light implies that time is relative; specifically, the time of a moving clock is dilated. 145. Describe what "length contraction" means in special relativity. 146. Define the Lorentz factor. Compute given a relative velocity between two observers. 147. Apply time dilation to compute the time between two events for different observers moving with different speeds. If gamma =10, and we each have identical clocks that tick once each second: at what rate do you think my clock ticks? At what rate do I think your clock ticks? Who is right? 148. Apply length contraction to compute the distance between two events measured by different observers moving with different speeds. If gamma =10, and we each have identical clocks: What size do I think your clock is compared to mine? What size do you think my clock is compared to yours? Who is right? 149. Explain the relativity of simultaneity, and give an example of simultaneous events in one reference frame that are not simultaneous in another reference frame. 150. Explain the twin paradox, and its resolution. 151. Explain the paradox of the "pole vaulter and the barn", and its resolution. 152. Explain the relevance of special relativity to muons hitting the Earth. 153. Know what quantities are constant and what quantities are relative in special relativity (e.g. x, t, c, p, E, m, c2t2-x2).