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Friday, October 12, 2012

Hours of Entertainment (Pew pew!)

Hey did you know underclassmen are almost as easy to entertain with laser pointers as kittens? It's true.

This challenge has had them going on and off for hours.

Hold this:

And move your body from one side of this board to the other:

while keeping the lasers on the stars. (There is a green Expo-marker star drawn on each side of the board.)

Other rules:
  • no changing the angle
  • hold the vertex against your sternum
  • always face the board, and no one stands between you and the board (safety, you know.)
A few of them are getting pretty good at it, so we appointed another kid to trace his path with chalk on the floor.

The children. They have some questions.

I know there are boring ways to get this point across with paper and pencil, but LASERS. THAT'S WHY.

Update: David Petersen made a Geogebra file to illustrate what is happening.


  1. They may have asked "what happens if I change the angle" right?

  2. Pew, pew, pewpewpew! Awesome. Very slick activity.

    1. Oh man I can't believe I didn't throw a few pewpews in there. This may call for edits.

  3. Yep Dan that was one thing. What about different angles. Um I don't know the answer to that yet sshhhh. An ellipse or something I'm guessing. I need to geogebra it up.

    1. Oh never mind it's just more or less of a circle. Thanks twitter.

  4. For the duller children in the group, could you offer a bit more as to what you're up to here? I'm apparently suffering from, "I may not be fast, but at least I'm slow" syndrome for a change.

  5. I think the converse would be more familiar. Inscribe an angle in a semicircle, get a right angle. This is trace a locus with the right angle locked in, get a semicircle.

  6. Nice. This is a much more memorable way to indroduce this topic.

  7. Awesome activity - the students must love it! Did you ask them what they thought the correct path would be first before they started to try it?

    Also liking John Golden's Geogebra File on this.

  8. oboyoboyoboy I like this. How can we code a simulation in Processing? What about if you have out of bounds on the ground? What about trajectories where you can't keep the lasers on? What about TWO sets of dots and kids standing back to back, what shapes work there? Eeeeeeee

  9. I don't know how you manage all that complexity. I admire it, I just don't understand. I feel like I have to keep it simple if the kids are going to take anything away.

  10. This is extremely cool, Kate.
    I'm doing this soon, and I'm definitely including the Questions by Dans Pearcy and Anderson.


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