Exam #2 Study Guide:

Exam 2 will have 40 multiple choice questions based on material covered in lectures 8 to 15. Material from HW #4-7 may be on the exam. A few of the questions will involve simple calculations, so you should bring your calculator. You will not need your clicker. You may bring one double-sided 8.5x11 inch sheet of paper with notes to the exam.

I Einstein and E=mc2

  1. Study the picture of the process of mass conversion to energy (page 4 of lecture 9).
  2. Know the fraction for the 5 classes of reactions (matter-antimatter, fusion, fission, chemical, mechanical)
  3. Be able to answer a question like: How many kg of uranium (fraction 0.001, fission) are equivalent to 10,000,000 kg of coal and oxygen (fraction 1E-10, chemical)?

II General Relativity

  1. Einstein developed the theory of General Relativity
  2. The main postulate is that we can’t distinguish gravity from acceleration in the opposite direction
  3. Space and time are combined into a 4-dimensional space time
  4. Mass warps space-time. What we experience as gravity is actually curved space
  5. Time slows down near a large mass. This is called gravitational time dilation.
  6. Time travel may be possible, but this leads to paradoxes that need to be resolved.

III Energy Conservation and Entropy

  1. Energy is the ability to do work. It is a scalar and is measured in Joules, J
  2. Know that energy is a conserved quantity
  3. Know the types and how to calculate them: Kinetic (energy of motion, ½ mv2), Potential (energy of position, mgh)
  4. Work = force x distance. Work converts energy from one form to another.
  5. Be able to use energy conservation to calculate the height or speed of something (an example is the LONCAPA problem)
  6. Power is the rate of change of energy: Power = Energy/time and is measured in Watts
  7. Be able to convert food energy to J and how to calculate how many Calories you burn walking up stairs. 1 Calorie = 1 kcal = 4184 J
  8. Thermal energy is random motion. More motion means higher temperature.
  9. Know the second law of thermodynamics – you can’t get something for nothing
  10. Entropy
    1. Is a measure of the number of possible states of a system
    2. The second law says in any process the entropy of a closed system always increases
    3. Know how to calculate the increase in entropy

IV Electricity and Magnetism

  1. Magnetic force: a compass has a north and a south magnetic pole. North poles are attracted to south poles; like poles repel.
  2. The Earth is like a big magnet with a south (north) magnetic pole near its North (South) geographic pole. All the planets and our Sun have magnetic fields.
  3. Electric force: like charges repel; opposite charges attract
  4. Charge is a property of matter. The fundamental unit is 1.6E-19C. This is the charge on a proton. An electron has a charge of –1.6E-19C. Note: quarks have fractional charge, but they are never observed free in nature.
  5. Be able to calculate how many electrons are or (or are missing from) an object.
  6. What happens to the size of the electric force if the distance is 2x greater; 3x greater; 10x greater?
  7. Know that moving charge is the origin of magnetic fields.
  8. Electric fields
    1. A vector measured in N/C or V/m
    2. Charge creates an electric field
    3. The direction of the field gives the direction of a forced on a + charge
    4. Force on a charge q:  F = q E   (E is made by another charge Q) [E=F/q]
  9. Electric Potential; V  (which is measured in volts = J/C)
    1. Be able to find E from V:  E = -DV/Dx. Electric field is the rate of change of electric potential with distance.
    2. Positive charge makes positive potential
    3. We can think of potential as hills and valleys. Positive charge rolls downhill negative charge rolls uphill.
    4. Be able to look at a graph of potential versus distance and tell the direction of forces, size and dire
  10. Circuits
    1. A battery is like a pump that raises charge up an amount V and the charge flows around the circuit.
    2. Current is the rate of flow of charge I = Q/Dt
    3. As charge flows in a wire heat is generated. This is how light bulbs produce light.
  11. Electric materials: Know the 4 types and their characteristics

V Quantum Mechanics Basics

  1. Electromagnetic spectrum (Radio, microwave, infrared, visible, ultraviolet, X-rays, g-rays)
    1. We see photons from 1.8 to 3.1 eV ( energy=hv; v is the frequency, h is plank’s constant)
    2. Know period, frequency, wavelength and the relation c=wavelength x frequency
  2. Inverse square law and how it explains the r2 dependence of the Coulomb force.
  3. Know that all objects in nature have particle and wave properties.
  4. Know that particles have a wavelength l=h/p. Be able to calculate a wavelength.
  5. All particles have a wave nature. The thing that is waving is probability.
  6. Waves can overlap, this is called interference.
  7. Uncertainty principle and be able to use it. Know both the DxDp and DEDt versions.

VI The 4 forces of nature

  1. Know the four forces and their characteristics from the table in lecture 15
  2. Be able to recognize simple Feynman Diagrams
    1. Two electrons, or protons, or other charges objects interacting via the Coulomb force
    2. A neutron (actually a down quark in the neutron) decaying to a proton (an up quark in the proton) by the weak force
    3. Two protons (or a proton and an neutron, or two quarks) interacting by the strong force
  3. Be able to check reactions for Baryon conservation, lepton conservation, electric charge conservation
  4. Know what the following words means: Field theory, Quantum Electrodynamics, Quantum Chromodynamics
  5. Know that Gravity is much weaker than the other forces and does not seem to fit in.
  6. Know that neutrinos interact by the Weak force, have mass, no charge, have lepton number, but don’t interact much.
  7. Antiparticles have opposite charge, baryon number, lepton number. When the meet with their like particle they annihilate giving off energy.
  8. Review the contents of the table of particles on page 9 of lecture 15