Pocket Crossbow

In this lesson, you utilize the stress of the popsicle sticks paired with the energy of the string to launch projectiles from a pocket sized crossbow. This project, while being a lot of fun to make and use, is also a doorway top the world of physics. While this project is not too difficult to build and can be adaptable to most ages, this Instructable was created for grades 9 and 10 due to the tools used. Since this is a simpler project try letting the students experiment with different materials or set up targets and see what builds operate the best based on certain catagories! There is a lot of opportunity for individuality, teamwork and creativity in this project.

Learning Objective:

Students will be able to create a pocket sized crossbow using easily accessible materials and explore design ideas through testing and redesigning.

Standard:

Standard 7: Design in Technology and Engineering Education 

• A highlight of this project is the opportunity for creativity. Having the ability to create different versions of this project allows students to showcase that there is no one way to design this project. By utilizing the design process, the students attain a solid understanding of this standard through this project.

Benchmarks:

• STEL-7P: Students weigh the benefits of their varying designs of material quantities and variants
• STEL-7T: Students access why they believe one design works "better" than another based on their knowledge of tension, pressure, and stress.
• STEL-7U: Students evaluate their peers designs through competition.

Practice:

There are a few practices that are showcased throughout this project but I think the one that is most prominent is creativity. The initial concept in of itself is creative, use common household items to create, a fun small sized toy. And while it is a toy, it does allow students to utilize their knowledge and creativity to change the project in their own unique ways to achieve new heights, sometimes literally.

Context:

Tension and stress are the most prominent contexts of this project. Students need to understand how to find a balance between the stress of the bow and the tension of the string to maximize velocity. A very nice physics lesson can be offered before and or after this project to bring light to what's going on behind the scenes. The same concepts can be applied to the projectile depending on what you use.

(The following list represents the items in the image from left to right, top to bottom)

• 8 popsicles sticks ($1.25 for a pack of 100)
• Sewing string ($1.25 for ~2ft) (again this material can vary to your liking)
• Sewing thread (~$0.50 for a medium spool)
• Scotch Tape (~$.75)
• Super glue ($1.25 for a pack of two)
• Scalpul ($1.25 for a set)
• Scissors ($1.25)
• Small Saw ($5.98)
• Ruler ($1.25 for a pack of 3)
• 7 cm long .5 diameter wooden stick ($0.33 for 3ft)(this is used for the bow, the material can be whatever you think might work)

This is approximately $12 per student at the absolute most ( most of the materials can be used by multiple students at a time and materials like thread have enough on a spool for the whole class. In addition almost all if not all the materials can be found in a school setting, so in some cases the cost of this project is $0.

This video is a step by step on how to make this project. You can start and stop it whenever you like, go at your own pace!

This is the final product! (note: the front end is cut off in the image. That is optional and for style purposes only, it serves no functional purpose).

As was probably noticed, there was no discussion regarding the projectile itself. That is because it is up to the students! In the video, a piece of leftover popsicle stick was used and it worked pretty well, imagine what would happen if some more time was spent on designing one?! As far is this actual step is concerned, it's optional. The students have created the project based on the video, but there is still more learning that can be done. Students can go back to the beginning of the video and try to use different materials or designs then what was shown, let the creativity flow, the opportunities are endless!!