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Dotted Line on Blackboard

  1. Jul 7, 2011 #1

    FeDeX_LaTeX

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    Hello,

    I have been watching a few lectures recently by Walter Lewin at MIT, and I've noticed that he draws dotted lines really quickly using only a piece of chalk and his hand. How does he do this free-hand so quickly? Does he just have a very fast muscle-twitch or is there a special technique of doing this? I have tried doing this on my whiteboard at home and I can't do it anything like the speed at which he does it.
     
  2. jcsd
  3. Jul 7, 2011 #2
    Is it the same Walter Lewin as this one?
    https://www.physicsforums.com/showthread.php?t=464025&highlight=lewin"
     
    Last edited by a moderator: Apr 26, 2017
  4. Jul 7, 2011 #3
    It's got to be the chalk skipping on the chalkboard. I once knew a guy that could draw practically perfect concentric circles free-hand. It was the most amazing thing I'd ever seen.
     
  5. Jul 7, 2011 #4

    jtbell

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    Chalk makes more friction against a chalkboard than a marker makes against a whiteboard. That friction is a useful tool for helping me "control" my writing. My writing during lectures became noticeably sloppier when we replaced our chalkboards with whiteboards.
     
  6. Jul 8, 2011 #5

    FeDeX_LaTeX

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    Hello,

    Thank you for the link. That is exactly what I was talking about. I would really like to try and see if I can figure out how to angle the chalk to produce that effect on a blackboard. Regarding the drawing of perfect circles, I also think this is very cool. I guess this is because the shoulder is a ball-and-socket joint.
     
  7. Jul 8, 2011 #6

    jtbell

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    Tip for drawing circles on the board (whether white or chalk): First draw the circle, then draw the dot for its center. It's a lot harder to center them properly when you do it the other way! :yuck:
     
  8. Apr 26, 2012 #7
    This guy demonstrates it very nicely. It's all about the angle at which you hold the chalk and the pressure you apply.
     
    Last edited by a moderator: Sep 25, 2014
  9. Apr 26, 2012 #8

    lisab

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    Necroposts mystify me.
     
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