Physics  120  MIDTERM  2  Study  Guide      

Fall,  2014 I.  Coverage:  Chapters  4  (just  a  little  bit),  5,  6,  14  -­‐17  (Homework  Assignments  4  –  7) II.  Please  go  over  

a) all  homework  problems,   b) all  questions  on  lecture  slides,   c) all  lab  reports.  

    III.    Practice  Questions  

  1. Where  does  nuclear  fusion  occur  in  the  Sun?  

  2. What’s  the  phase  of  matter  in  the  Sun?  

  3. How  does  the  energy  produced  at  the  core  of  the  Sun  get  transferred  to  the  surface?    

4. What  is  the  average  temperature  of  the  surface  of  the  Sun?    

5. What  are  the  axes  of  a  Hertzsprung-­‐Russell  (H-­‐R)  diagram?    And  on  a   Hertzsprung-­‐Russell  diagram,  where  would  we  find  red  giant  stars?    

6. What’s  the  apparent  magnitude  of  the  faintest  star  visible  to  the  naked  eye   under  the  best  possible  conditions  on  Earth?    

  7. How  old  is  the  Sun?    

  8. How  did  the  nuclear  fusion  reaction  in  the  Sun  start  initially?      

  9. In  a  dark  room,  a  red  rose  under  a  green  light  would  appear  as  what  color?  

  10. How  does  the  apparent  brightness  of  a  star  change  with  distance?  

  11. What  are  the  stellar  spectral  types,  from  highest  to  lowest  surface  


12. What  is  the  Sun  made  of?    

13. What’s  the  luminosity  of  a  star?    What’s  the  apparent  brightness  of  a  star?      


14. What  are  the  apparent  magnitude  and  the  absolute  magnitude  of  a  star?    

15. What’s  the  diameter  of  the  mirrors  for  the  world’s  largest  optical  telescopes?    

16. How  does  the  mass  of  a  star  affect  its  longevity?    

17. What  counterbalances  gravity  in  brown  dwarfs  and  white  dwarfs?    

18. What  is  antimatter?    

19. What  is  the  greatest  mass  a  newborn  star  can  have?  And  what  kind  of   pressure  prevents  stars  of  extremely  large  mass  from  forming?    

20. How  many  high  ocean  tides  do  we  have  due  to  the  gravitational  force  of  the   Moon?    

21. How  doe  the  kinetic  energy  of  driving  at  30  mph  compare  with  driving  at  15   mph?  

  22. How  doe  the  momentum  of  driving  at  30  mph  compare  with  driving  at  15  mph?    

23. How  would  you  describe  degeneracy  pressure?    

24. You  can  say  we  are  all  “star  stuff”  (or  star  dust);  why  is  that?    

25. When  does  a  star  become  a  main-­‐sequence  star?        

26. How  does  a  main-­‐sequence  star  regulate  its  own  temperature  and  size?    

27. What  are  the  major  stages  of  life  for  a  low-­‐mass  star?    

28. What’s  the  energy  source  for  the  Sun?    

29. What  would  you  see  if  you  look  at  a  white  light  source  through  a  prism?     (Don’t  look  directly  at  the  Sun,  except  through  the  right  kind  of  filter!!!)    

  30. Consider  two  pucks  with  same  mass  sitting  on  the  surface  of  ice,  where  friction  is  negligible.    One  puck  moves  at  a  constant  velocity  of  v.    It  then   collides  with  a  second  puck  head-­‐on  and  stops.    What  must  the  velocity  of  the   second  puck  be  after  the  collision?  

  31. What  is  the  meaning  of  E  =  mc2?      

  32.  What’s  room  temperature  in  °F,  °C  and  K?  


33. What  is  the  wavelength  of  a  wave?    

34. Photon  1  has  longer  wavelength  than  photon  2.    How  do  their  energies,   frequencies,  and  speeds  compare?  

  35. What’s  the  difference  between  potential  energy  and  kinetic  energy?    Give  two  examples  for  each  kind.    

    If  there  is  time,  I  will  answer  individual  questions.    

Final Exam Study Guide I. Coverage: Chapters 1 – 6, 14 – 20, 22 – 23. II.  Please  go  over      

a) Study  guides  for  Midterms  1  and  2,  for  the  Final  Exam,  and  the  review   questions  on  slides;  

b) All  homework  problems;   c) All  questions  on  lecture  slides;   d) All  lab  reports;  

in that order. III. Practice Questions

1. What is the average temperature of the surface of the Sun?

2. How long does it take for light from the Sun to reach Earth?

3. Why do astronauts in the International Space Station feel weightless?

4. Where does nuclear fusion occur in the Sun?

5. One morning you see the Moon at its highest point in the sky as the Sun is about

to rise. The Moon will appear as

6. What’s the phase of matter in the Sun?

7. List three pieces of observational evidence for dark matter.

8. What are the axes of a Hertzsprung-Russell (H-R) diagram? On a H-R diagram, where would we find white dwarfs?

9. What’s the apparent magnitude of the faintest star visible to the naked eye under

the best possible conditions on Earth?


10. How old is the Sun?

11. How did the nuclear fusion reaction in the Sun start initially?

12. What is the total number of galaxies in the observable universe?

13. How does the apparent brightness of a star change with distance?

14. What is the meaning of E = mc2? How can this equation be fully realized?

15. What is the Sun made of?

16. What prompted astronomers and astrophysicists to propose the existence of “dark energy” since the late 1990’s?

17. What’s the luminosity of a star? What’s the apparent brightness of a star?

18. How does the mass of a star affect its longevity?

19. What counterbalances gravity in brown dwarfs, white dwarfs, and neutron stars?

20. What is antimatter?

21. How doe the kinetic energy of driving at 30 mph compare with driving at 15 mph?

22. Why can’t the cosmic microwave background (CMB) radiation be perfectly

uniform everywhere?

23. True of False: The rotation of nearly all large objects in the solar system, the Sun, the planets, and large moons go from West to East.

24. What does Hubble’s Law state?

25. What is gravitational lensing?

26. One evening, at 8 PM, a crescent Moon is setting. The next evening at 8 PM, will the Moon appear smaller or larger compared with the previous night?

27. You can say we are all “star stuff” (or star dust); why is that?

28. When does a star become a main-sequence star?

29. What is the wavelength of a wave?

30. What are the major stages of life for a low-mass star?


31. What do massive-star supernovae leave behind?

32. What do white dwarf supernovae leave behind?

33. Iron is at the end of the line for nuclear fusion processes in stars. How and where

are heavier elements made?

34. What’s the White Dwarf limit? And what’s the significance of it?

35. How does a white-dwarf supernova happen?

36. What is redshift? What is blueshift? How do you determine whether a galaxy is moving away or toward us?

37. What’s a black hole?

38. What happens when an electron in an atom goes from a higher energy state/level to a lower energy state/level? From lower to higher?

39. What is the size of the event horizon of a stellar mass black hole? How does the size of the event horizon of a black hole vary with its mass?

40. Roughly how big is the Sun, a planet, a typical dwarf planet, a typical asteroid,

and a typical comet?

41. The longest day in a year on Earth happens on: spring equinox, summer solstice, fall equinox, or winter solstice?

42. What observational evidence do scientists have of the existence of black holes?

43. Photon 1 has longer wavelength than photon 2. How do their energies, frequencies, and speeds compare?

44. Suppose you built a scale-model atom in which the nucleus was the size of a pea. About how big would the atom be?

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