Catapult and Trebuchet Challenge

Purpose:

The purpose of this challenge project is to provide students a hands-on application of the principles and applications of projectile motion.

The Challenge

To construct a trebuchet/catapult capable of hurling its projectile further, and with more accuracy, than any other trebuchet in the class on two different levels:

Level 1

Construct a catapult from lightweight materials, including cardboard, paper clips, glue, tape and string, capable of hurling an object a distance of 20 feet.

Level 2

Construct a trebuchet from PVC and other materials that will be capable of hurling a tennis ball up to 100 feet.

Extension

Process

Research history and use of catapults
Brainstorm catapult design by sketching out plans on grid paper
1. Design will need to be approved before you starting cutting PVC
Share your idea on Flipgrid https://flipgrid.com/0aggxrn
Construct catapult(completed in class)
Document design process in Flipgrid
Test your catapult for distance, accuracy and precision

Before you build you need to have a design of your idea. It must include the following concepts:

The top of each page should include your name and name of trebuchet
A diagram of your trebuchet design
1. Include measurements of each piece of pvc to make sure you have enough materials
2. Label whether joint is 90, 45, T, or cross PVC piece

Materials

3 x 10 foot ¾ PVC
10 x ¾ T Shape PVC
8 x 45 degree ¾ PVC
1 x 1” Cross PVC
1 x 1” PVC Caps
1 x 1” T Shape PVC
Piece of hanger for trebuchet cap release
Tennis ball
Duct tape for pouch

Resources to Explore

How does a catapult work?
Catapult History and Modern Day Construction
History of Catapults
Catapults – many examples to build
Build a Simple Trebuchet from Household Items
Energy Transfer in Trebuchet
How does a catapult work? – Podcast
http://www.virtualtrebuchet.com/
http://thehurl.wikidot.com/trebuchet:trebuchets
http://www.real-world-physics-problems.com/catapult-physics.html
- The onager catapult is almost identical to the trebuchet, but instead of a falling counterweight, it uses a torsion bundle to rotate the arm (similar to the mangonel, described previously).
Trebuchets History
Discovery Channel Videos: Time Warp: Counterweight Trebuchet

Ideas to Consider

Trebuchets are the superior siege weapon and can launch a 90 kg projectile over 300 meters
Dynamics of motion
immediate velocity at the point of release
Trajectory basics
Leverage
Swinging basket vs static weight on the arm
Centrifugal force
Principles of finding the optimum range (45°) launch angle by experiment, then mathematically with trig and vectors, then looking at application in siege weapons
Fun fact, 45° is actually not the optimum launch angle. The optimum launch angle varies with the coefficient of air drag on the body. If students throw a wadded up paper, a stone, a lead fishing line weight, and a cork, they will see different optimum angles to throw.
Cube-square rule

Standards

Next Generation Science Standards Grades 3-5 (Ages 8-11)

Motion and Stability: Forces and Interactions
- Students who demonstrate understanding can: 3-PS2-1. Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object.
Engineering Design
- Students who demonstrate understanding can:
  - 3-5-ETS1-1.Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.
  - 3-5-ETS1-2.Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
  - 3-5-ETS1-3.Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
Next Generation Science Standards Grades 6-8 (Ages 11-14)
- Engineering Design Students who demonstrate understanding can:
  - MS-ETS1-1 Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.
Principles and Standards for School Mathematics (ages 11 – 14)
- Measurement Standard -Apply appropriate techniques, tools, and formulas to determine measurements.
  - solve simple problems involving rates and derived measurements for such attributes as velocity and density.
Principles and Standards for School Mathematics (ages 14 – 18)
- Measurement Standard – Apply appropriate techniques, tools, and formulas to determine measurements.
  - analyze precision, accuracy, and approximate error in measurement situations

Progression

Step 1 – Tic Tac Catapult

Step 2 – PITSCO Catapult

Insert Sketchup to design catapult

Step 3 – PVC

*Final challenge water balloons or small pumpkins

Furthest distance
Accuracy of Targets
Community Challenge

Other Ideas

Home Depot PVC Water Balloon Launcher – http://blog.homedepot.com/3-pvc-projects-to-keep-your-kids-cool-this-summer/

Examples of Learning

We had another very successful night of Ancient Engineering Class. Students expanded their expertise in making catapults. In our first class we build a catapult design to launch Tic Tacs(tutorial coming soon!).

In our second class we had two goals:

You can watch a YouTube video of me explaining the reasons behind class 2 as well as students in action.

1. Understand key components required for a successful catapult

2. Design a catapult from scratch based on experiences

For this class we used the PITSCO catapult. This catapult took a bit longer than anticipated, but that is perfectly okay. I would rather have too much than too little. Students had to really work through not only following instructions, but understanding spatial reasoning of looking at an image and making sense of it in the real world.

Spatial reasoning and using glue were two skills that were developed. Both of these were skills that the students had to really upgrade in this project. It was a moment of insight for me as an instructor to make note of the idea that we cannot assume prior knowledge of use of materials no matter how common. This was really powerful for me to witness going forward as we begin our final build of a PVC trebuchet.

The students were focused. They worked to get their catapults functional and once they had it working we began to experiment with what leads to the farthest launch.

I had a tape measure of 16 feet thinking this would be plenty for the catapults. It did not take long for them to use the Play-Doh we were using as ammo dialed in to the right size and weight to maximize launch. This was followed up with creating more tension in the rubber bands which creates more potential energy by twisting the bands, adding more rubber bands, and sampling different types of rubber bands.

Before long we had objects clearing the entire room, launching up into the ceiling, and more. If only we had more daylight to take the outside to measure real distance. It was awesome watching them figure out how to make it work best.

Just like our first class the 90 minutes flew by. Students kept their catapults and some were able to design their own styles if they had time.

It was another successful night. I love working with kids who love learning. It is what makes me love being an educator. While I no longer have my own classroom, this space at 212 STEAM Labs provides me my classroom space to do the teaching the way I love and know works. The kids are so into their work that many don’t want to leave.

As we head into our final two weeks of this course students will begin to design their own PVC trebuchet. They will be given specific materials. Nothing more. They will have to sketch their plans and have it approved to make sure they have proper materials before they cut. Once they start cutting their parts there is no turning back.

If you are interested in learning about the next project components make sure you stay tuned. I will be posting the document and guidelines soon. You can also join our community event on October 1st where we are hosting a weekend challenge of making a PVC trebuchet. .

Now it is back to work to fine tune some new designs. If you are checking things out from home, then make a catapult with your own household supplies. Send your work our way. We would love to see what others are making.

Finally, I will be building out Coffeechug Catapult 2.0 this weekend. If you want me to test out your ideas to make version 1.0 better check out the video and send me your ideas.