1 / 8

Announcements 12/3/10

Announcements 12/3/10. Prayer Wednesday next week: Project Show & Tell 5 extra credit points for volunteering, 10 points if I pick you Applications due tomorrow night; 5 volunteers so far Lee’s program: see email TA ratings: see email Survey about Optics HW problems: extended until tomorrow

lorainek
Download Presentation

Announcements 12/3/10

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Announcements 12/3/10 • Prayer • Wednesday next week: Project Show & Tell • 5 extra credit points for volunteering, 10 points if I pick you • Applications due tomorrow night; 5 volunteers so far • Lee’s program: see email • TA ratings: see email • Survey about Optics HW problems: extended until tomorrow • Definitions: Lorentz transformations: or also

  2. Worked problem #1 • Four “simultaneous” events: viewed by Earth, (x, ct) = … • (0.5, 2) • (0, 2) • (-1, 2) • (-2, 2) • Dr. Colton’s rocket comes by going 0.5 c in the positive x direction. Where/when does he measure these events? g = 1.1547, bg = 0.5774 a = (-0.5774, 2.0207); b = (-1.1547, 2.3094); c = (-2.3094, 2.8868); d = (-3.4642, 3.4642) Lee’s program

  3. Worked problem, cont • Some things to notice: • “Linear” transformation: Notice that lines transform into lines • This case: downward sloping line. There will be some point having ct=2, that (in B’s frame) is at negative time! • Let’s try transforming point “e” = (6, 2) • Turns out… • If a point is outside the light cone (“spacelike”), you can always find some observer that sees it happen at a negative time. • If a point is inside the light cone (“timelike”), then no observer can see it happen at negative time. • Causality! point “e” = (5.773, -1.155)

  4. Worked problem #2 • Lee is running past Cathy at b = +0.5 (g = 1.155). He passes her at t = 0. Cathy is holding the left end of a meterstick, length = 1 m. • In Cathy’s frame: draw the world lines of Cathy, Lee, and the right end of the meterstick. • In Lee’s frame: draw the same worldlines. Lee’s program

  5. Velocity transformations • Lee is standing on a train going past Cathy at +0.5 c. John is also on the train, running past Lee at +0.5 c. What is John’s speed relative to Cathy? (NOT 1.0 c!) • First: draw diagram from Lee’s frame • Then: transform to Cathy’s frame • Find slope of new line (which is inverse of b) • Result: vJohn-Cathy = 0.8 c • General formula: Use this instead of book eqns 39.16 and 39.18. Far simpler; works every time! Caution: terms are sometimes negative. (Don’t need to know transverse velocity formula, eqn 39.17.) Compare to “Galilean”: “1-3” = “of object 1 with respect to object 3”

  6. Worked Problem #3 • HW 39-2 (the one that got canceled) 0.99687 Answers: (a) 53.0; (b) 0.083; (c) 53.0

  7. Worked Problem #4 • Optional problem from HW 40

  8. Worked Problem #5 • Optional problem from HW 40

More Related