MnSTEP Teaching Activity Collection > MnSTEP Activities > The physics and engineering of a trebuchet

# The physics and engineering of a trebuchet

#### Summary

In this simple machines lab students will investigate how the trebuchet works using their prior knowledge of simple machines, and physics. Students build a trebuchet in groups of their peers, and analyze the physics and engineering that goes into building it, and launching it. Each student in the group has a specific job description, and is responsible for those duties. A copy of the job descriptions is provided.

## Learning Goals

This activity is designed for students to investigate the engineering and simple machines that go into constructing, and launching of a trebuchet. The students will use critical thinking skills when constructing, and launching the trebuchets. The students will learn how to manipulate, and change variables to get to a goal of hitting a target, or going a specific distance. Students will understand the concept of kinetic energy, and how to calculate it, as well as figuring out how much mass is needed to throw a specific distance. Vocabulary words discovered: Arc, Diameter, Fulcrum, Gravity, Kinetic Energy, Mass, Potential Energy, Reengineer, Trajectory, Trebuchet, and Velocity.

## Context for Use

This activity has been used in both a seventh grade level, and sixth grade level, but can be adapted for elementary or high school students as well. You can make this project as hard, or easy as you would like! This activity is a lab that takes anywhere from 6 days to 10 days (55 min class lengths). You will need trebuchet kits, which can be ordered from www.pitsco.com. You want to make sure that the students have a good background of the vocabulary terms listed above prior to beginning this activity. This activity is can be done during a simple machines unit, engineering unit, or physics unit.

Subject: Mathematics, Physics:Classical Mechanics
Resource Type: Activities:Lab Activity, Classroom Activity
Grade Level: Middle (6-8)

## Description and Teaching Materials

Prior to starting this activity you want to make sure that you have covered an introduction to simple machines.

Materials needed: Trebuchet kits (purchase from www.pitsco.com), Trebuchet teachers guide (also can be purchased from www.pitsco.com), "Medieval Siege" video (can be ordered from www.nova.com)

Introduction: Talk about the different types of simple machines, as well as some physics terms (see the vocab words listed in the "goals" section). There are a couple of PowerPoint presentations attached that you can use for an introduction. I also show them the "Medieval Siege" video prior to starting the construction. This video will give them a great background of trebuchets, as well as some ideas on how to change the trajectory, and velocity of their ball when it is launched.

Procedure:
1. Divide your class up into groups of 3 or 4 (no more than 4 in a group, you will see why later). Try and put them into groups keeping in mind you want to have somebody in each group that is assertive, and a couple of passive students as well.
2. Pass out Trebuchet group jobs sheet (see attached).
3. Go over the description of the jobs with the students.
4. Have students select which job best fits their personality (be sure you emphasize they can't switch jobs once they have picked one!)
5. Have the direction reader in each group come up to you and get the supplies they need as each item comes up in the directions. REMEMBER, ONLY THE DIRECTION READER MAY COMMUNICATE WITH THE TEACHER!
6. As each group completes their trebuchets have "challenges" set up for them. There are a couple good ones inside the "trebuchet's teachers guide" book which can be purchased at www.pitsco.com, or you can come up with some of your own as well. You can make the challenges difficult to fit high school students, or make them a little easier for elementary students as well. Trebuchet Group job descriptions ( 22kB Sep9 09) Simple Machines power point (PowerPoint 593kB Sep9 09) Trebuchet vocab words (PowerPoint 546kB Sep9 09) Sample of trebuchet teachers guide (Acrobat (PDF) 84kB Sep9 09)

## Teaching Notes and Tips

Remember, as the teacher you hold control of the class (duh!), but each group has their own leader (direction reader). When I do this activity I make sure that the kids are doing the project, and not ME! It is important to let them discover how to put the trebuchet together as a group, without the teacher's guidance. Having the students do the project completely on their own teaches them group working skills, as well as problem solving skills. You will find all the groups will have a working product at the end, you just have to force them to know that they can do it on their own! Creating this activity is a great addition for any classroom. It is a good activity to use some of our new engineering standards! It is way different from the normal activities you might do (as I found out when I started doing it!), it's a great way to get your simple machines unit hands on!

## Assessment

There are many different ways to assess whether or not your students have mastered the information given to them. I put questions about the trebuchet, and it's history on the final exam for the simple machines unit. The main assessment isn't something that is done on paper, it is the final product of the activity. If the group has successfully put together a trebuchet that can launch a clay ball forward, they have mastered this activity. You could also assess them on whether or not they successfully measured the kinetic energy of the ball being thrown, or calculated the amount of potential energy their ball has prior to being thrown.

## Standards

Standard 1.2.2 Engineering design is the process of devising products, processes and systems that address a need, capitalize on an opportunity, or solve a specific problem.
Standard 2.2.1 The motion of an object can be described in terms of position, direction, and speed.
Benchmark 6.2.2.1.2 Graph an objects position
Benchmark 6.1.2.2.1 Apply and document an engineering design