# Dotted Line on Blackboard

1. Jul 7, 2011

### FeDeX_LaTeX

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. Jul 7, 2011

### Jimmy Snyder

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
3. Jul 7, 2011

### timthereaper

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.

4. Jul 7, 2011

### Staff: Mentor

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.

5. Jul 8, 2011

### FeDeX_LaTeX

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.

6. Jul 8, 2011

### Staff: Mentor

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:

7. Apr 26, 2012

### RubyHeart

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
8. Apr 26, 2012

### lisab

Staff Emeritus
Necroposts mystify me.

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