I love introducing STEM projects (like these catapults) to my 8th grade students. Because this is the third year I have taught most of the students, they know my rules, and I know their tendencies. By this time, I can foresee some problems that the students could run into and avoid them. I can also try new things with these students. They won’t have melt-downs if something doesn’t go as planned! I’m also continually impressed with how many cool ideas and designs they come up with… they are very creative!

These eighth graders recently wrapped up a unit on forces and simple machines. Last year, I saw a few lesson plans that involved building catapults and thought that would be a perfect way to tie everything together. The project went fine, but students didn’t quite use the simple machine concepts like I had hoped they would. So this year, I decided to amp up the catapult plan and make better! These eighth graders love a challenge and could roll with any minor surprises!

Lesson Overview

First, we discussed a little bit of catapults history. Together, we talked about the different types that were used for various reasons. Accuracy, power and distance are all important features of a quality catapult. Knowing this information, students received the challenge to design and build a catapult that would meet the three main criteria. Launching mini marshmallows as far as possible, trying to accurately shoot the marshmallows into a bucket, and using a sugar cube to knock down stacked cups were their tasks.

The catapults were a huge hit! The kids wanted to bring in materials from home to work on them (which I didn’t allow), and had unique ideas of how they wanted their catapults to work. I will say that next year, I will have to give a few more design restrictions. Some of the created designs had difficulty with one or two stations. Trebuchet type catapults seemed to work the best for the stations I choose.

Overall, I would say this year’s catapult project went much better than last year’s. I made sure students had to identify the simple machines in their design, and even calculate the mechanical advantage. Next year, I will adjust it more (aren’t we as teachers always tweaking our lessons–even the successful ones??) but I would say this project is a keeper!

Materials to use:

Popsicle sticks, spoons, rubber bands, various sizes of cups, tin cans, toothpicks, duct tape –really anything you can find that you think will work!

Other things you may need:

Cups to stack for the power station, sugar cubes (can be used for harder projectiles), meter sticks, a container for the accuracy station, and tape for starting lines. Use this worksheet packet as well – CrazyCatapults.docx. I adapted this from TryEngineering.org and from Vivify’s site. Both these sites contain great ideas for STEM challenges and activities and you should check them out!

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