# Catapult Contest!

Hold a contest:
To throw a “regulation” paper ball a distance. Set up a measuring tape or multiple yard/meter sticks and have line judges watch when the ball hits the ground. A whole host of scientific data analysis can crop up out of this part of the activity. You can perform several trials and even have a discussion on the purpose of trials and what constitutes enough trials. Students can do some statistics to see the reliability of each machine (mean, median, mode).

A regulation ball can be decided upon and made. This reduces the number of variables the machines have to deal with if they are all throwing the same type ball.
There really are a lot of learning opportunities in just letting a unit or investigation grow out of something your kids get excited about. Don’t be afraid to just drop what you are doing and get on the floor to figure things out with your kids. Our kids had a great time watching the building and performance of these huge machines over Thanksgiving. It was really amazing to watch all the work that goes into winning this contest! The kids asked a lot of good questions and got me thinking.
One of the best things about this is being willing to say yes when the kids ask if they can do it themselves. Plenty of information is a few clicks away and it doesn’t cost anything to begin a process and learn with your kids.
Thanks for joining in for the catapult fun! May your homeschool days be filled with adventures and exploration!

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# Catapult Physics!

Physics:

Simple Machines- this is a great chance to discuss simple machines but in particular, the lever. Catapults and trebuchets use a lever to do work. Students can research the different classes of levers and see how changing the placement of the fulcrum changes the performance of their machine.
Similar to the mechanics of the machines, how does the machine do the work? They all transfer large amounts of potential energy into kinetic energy. Some do it more efficiently than others.

• Which one works best?
• How can you test it?
• Make the hypothesis and make plans to build the machine so you can test it!

For older students, there are all sorts of calculations you can do on the energy efficiency of the machines. In a quick search, I found a website dedicated to Experiments with Trebuchets. The author, Mr. Bullock, gives plenty of instructions and advice on building the trebuchets and has an entire section on the math. All the variables are listed in working out the formula for the Energy Efficiency which is the Kinetic Energy/Potential Energy. Of course you’d need to derive the numbers for Kinetic and Potential Energy which would be great fun using the list of variables provided. I may not be right on target with my answers, but admittedly I have a curiosity about physics and math so this is something I’d encourage my older children to try!
Again, this unit study isn’t about exhausting all the planning tools you have. It’s about getting your students excited about an exploration and not worrying if everything is in place first. It’s about a quick web search and doing and having fun.

Tomorrow, we’ll have a contest to see which catapult performs the best!
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# Build a Catapult!

Build It:

Find and use materials to build a mock up of the machine. So far, my kids have been successful with a LEGO catapult and have discussed how they could use the LEGO NXT (or EV3 which was just released) kit to make another type of machine called a centrifugal- which needs a motor. Of course you can find kits to build catapults and trebuchets (this one is picture above).

An old “standby” I have used often (as a classroom teacher as well) is the shoebox catapult.
For shoebox catapults you’ll need:

• a shoebox
• pencils (or other strong stick)
• rubber bands
• egg carton cups

I’d love to tell you more, but then that would take away the opportunity to figure it out! Remember, part of this unit study is just to let your kids explore and discover. Feel free to give pointers or ask questions of your student to help them along. Have the kids plan and make sketches. In my classroom days, I gave a recipe for how to build it and the kids did the work. How much more valuable to design it on their own!
Have fun with the building process- you can choose to give a parameter of time or you can simply let the process run out. Tomorrow, we’ll talk about the physics of siege engines. Join me!

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# The Mechanics of a Catapult {Day 2}

The rock hills, taken and shaped by hard work,
Are made to soar forward from the sling of a machine;
Through wind and clouds they ride upon their way,
Like Meteors they thunder through space
- Unknown Chinese Poet, 1300

Mechanics:
How are the machines constructed?
What materials can we use for our model for it to function properly?
How does the machine work?
One resource we love at our house is The Art of the Catapult by William Gurstelle. It’s a fun source of history and mechanics all rolled into one.

One of the pleasures of this unit study is to allow your children to immerse themselves in discovery. While they might enjoy some mentoring, don’t feel like you need to micromanage this study.

The next step is for them to build their own, so they have some fun motivation for finding out more about catapult construction. There are many online resources only a Google search away for detailed pictures, plans, and descriptions for catapults. Students can make sketches and make plans for materials they have around the house which would be suitable for creating their own catapult.

Reading and understanding how the machines work, will give students ideas on what materials to use and how to put them together. Enjoy this day of discovery!

Join me tomorrow and we’ll find out more about building these machines.

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# Catapults {A Five Day Unit Study}

After an inspiring two days of TV fun with the World Champion Punkin Chunkin on the Science Channel, my kids and I decided it might be fun to learn more about the machines these teams used to hurl their orange fruits- with the idea that we’d hurl something of our own, of course.

So, a rather impromptu unit on the physics and history of siege warfare machines was born!

Much of the design of this unit goes along with my “Science as Investigation” approach. The ideas that follow came out of a desire to dive right in and explore. Sometimes you don’t need the perfect curriculum or the perfect materials. You just need a question to be answered or something you want to figure out.

This unit will attempt to answer the question: What were these machines and how were they used? Who used them? How do they work? Can we build one? And how will it perform?
Day 1′s Topic?
Types of Siege Machines:
Catapults- research the different kinds of catapults and how they operated. When and how were they used? (I was able to find torsion and Roman models in my brief search)
Trebuchets- research the various models of trebuchets including the modern, “fixed axel” trebuchet which drops the counterweight straight down using the potential more efficiently. Trebuchets differ from catapults because they use a counterweight to throw the arm and hurl the object.
Without much preparation on your part, just send the kids off to see what they can find out. No special notebook pages necessary! Have them jot down their list on a sheet of notebook paper and make some sketches.
Join me tomorrow and we’ll find out more about these machines and how we’ll put that information to work later in the week.

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