Friday, September 10, 2010

Pimp My Catapult

*Fffwwwooooooooooooooooooosssshh* That is the sound of me blowing the dust off of my blog. Welcome back to my little corner of the Interwebs. Between getting married, buying a house and my math programming side project I've had little time to share anything on here, but I'm back in action and ready to start updating more regularly, so here we go...

I've been tweaking my catapult design a bit each year, and think I've finally found the best design to fire accurately(even in student hands).  So if you tried the catapult project last year, but had trouble with student accuracy this post might help if you're willing to give it another shot. If you haven't tried the project yet but want to this year, I would highly suggest using the design and tips below.  Here is the new design:

1)   Mini clothespins give a more appropriate distance and height.

2)   I now make the basket out of a thin strip of paper, complete the circle with a small piece of scotch tape and use a bit of glue to hold the basket on.  Having a basket that is just barely bigger than an m&m laying flat helps accuracy.  Make sure students know to load the m&m laying flat each time. 

3)   Cut off the rounded edge of the popsicle stick behind the basket.  The flat edge helps fire more consistently.

4)   This new firing mechanism allows student to essentially just pressing a button to fire.  There is still room for some error here, so make sure they know to hit the button SLOWLY each time. The back clothespin is positioned so that it just barely overlaps the back of the catapult when it is all the way down.  Here's a close up with the catapult loaded:
 5)   The front of the catapult is tilted forward so that it goes further and not as high.

6)   Okay, so there's no 6 on the picture, but thinking about it now it would make more sense to move the guide rails on the main catapult much closer to the back.

So there you have it. I hope this helps.  Let me know if you have any other ideas for improvements in the comments.

Previous catapult posts:

BONUS:  I let one of my classes build their own catapults last year, and after finishing the project one group decided to come in to my classroom during some free periods and make this ridiculously awesome trebuchet.


  1. Thank you for your posts and your inspiration! I took your catapult design and assignment and created my own quadratics lesson based on what you had done. One thing that we did differently was how we went about getting our equations to model the projectile's path. We flung M&M dipped in water then baby powder against cardboard covered in black butcher paper to get a couple dozen of so (x,y) pairs. From this we were able to do quadratic regression on our calculators (TI-84) and also do an eye-ball best fit parabola then writing a best fit quadratic model using inverse matrix equations. It was a lot of fun for me and all the students. Thanks!

    1. I'd love more information on your modifications!

  2. Jim from acrotech Great ideas! I am interested in using this, but I can't find your evaluation rubric referred to in an earlier comment on your first Catapult blog. Do you have a rubric and can you tell me how to access it? Thanks.

  3. Wow! It's awesome. I'll use this next year for energy conversions with my Intro to Physics class. fizix teacher in MT

  4. I love the idea of this project and really want to try it out on my Algebra 2 class this year, but I too am unable to find the grading rubric that was referred to earlier. Is there any way that I can get a copy?? My email is

  5. Awesome idea! I used it for my classes catapult project.

  6. I'm just stumbling upon this! What a fantastic project and great idea! I too am unable to find the rubric. Is there a way to access it or have it e-mailed to me?! I'd love to do this with my Algebra 2 classes!

  7. Hello - can I have the rubric too? thanks