Introduction: The Similar Triangle Rocket project is a group activity that focuses on the application of right and similar triangles as applied to rocket flight.

Timing: This project requires 60 minutes of class time to construct the rocket and 60 minutes to complete the activity. Break it up over four periods.

Group Size: Group and Individual

Learning Objectives: The objective of this activity is to:

a) Review right and similar triangles

b) Use students’ understanding of triangles to investigate path a rocket

c) Integrate a creative and competitive component into a traditional math lesson

Guiding Questions:

How can various types of linear equations be incorporated into a flipbook?

Materials: There are two components of this project: rocket construction and the similar triangle activity.

Rocket Construction – 2-Liter soda bottles, box cutter, scissors, cardboard, hot glue gun and glue sticks, duct tape, manila folder, scotch tape, markers and paint for decoration.

Similar Triangle Activity – Inclinometers (constructed by students), trundle, bottle rocket launcher, tire pump w/psi gauge, water container, graduated beaker, ruler, and protractor

Photocopy enough activity sheets for each student and enough inclinometer construction sheets for each group.

Ordering Resources:

Trundle

Launchers

1)

• Easy to use, but not particularly stable and you will swamp out a spot
quickly and have to move the launch site

2) ? - This is what I use. Very easy to set up and use.

Procedures:

This project is really three parts: rocket construction, rocket firing and the similar triangle activity. The procedure will look at each section individually:

Rocket Construction:

Building the rockets will require two 45-minute blocks, including the initial presentation. As a class, discuss the basics of rocket construction. The PowerPoint presentation covers the bare minimum for designing a functioning rocket. An Internet search of “soda bottle rockets” will provide a multitude of information on how to build and design these things. The main points are the weighting, the nose cone, and fins. Weighting the rocket is crucial. If the center of mass is not higher than the center of pressure, the rocket will tumble. A good rule of thumb is somewhere between 100-200 grams in the nose cone. The nose cone can be a simple cardboard, or you can get really creative and use a reshaped bottle called a guppy. Most students choose to just use the nozzle end of a cut 2-L bottle as the nose cone. Pictures of the various designs can be found in the PowerPoint presentation. The fins can really be any shape as long as they are not upward sweeping. Symmetry and spacing is the key with fins. There are obviously other parameters to consider, but for the purposes of this activity, we are just shooting for a functioning rocket.

The PowerPoint includes the contest component of the rocket activity. This could be removed, depending on your learning objectives. The contest adds a bit more excitement to results of the standard math activity. It is a great way to get wider range of students to shine.

At some point in time during the construction time, the group should build its inclinometer.

Rocket Firing:

Firing the rockets is the most exciting part, but it is also the trickiest. Have students practice pulling the cord before the actual launch. They need to give a sharp low pull along the axis of the launching pin. MAKE SURE THEY CANNOT PULL THE ROCKET TOWARDS THEM DURING LAUNCH! The bottles can be pressurized up to 100 psi, but this gets very dangerous. I fire at 40 psi with younger students.

Note: Rockets can be dangerous. Spend some time testing the firing process before launching with students, never over-pressurize, always wear and have students wear goggles, keep students out of the landing area, and don’t let students sit down (in case they need to run).

Similar Triangle Activity:

Read through the opening sections as a class. This part of the activity is individual, so students may have varying levels of competence with right and similar triangles.

Using the graph paper provided, students must choose an appropriate scale for the base. Try and have them maximize the use of the graph paper by choosing the largest appropriate scale. After they draw their base, they must use the launch angle (q) to construct a right triangle. Once the triangle is constructed they should measure the height and convert it to meters using the graph scale. They now need to add in the average eye level of the inclinometer readers. This is the total vertical height of the rocket. We study a little bit of trigonometry, so I have them check their results with the tangent function. Not a normal topic for Pre-Algebra, but certainly within their grasp.

Assessment: Student’s Similar Triangle Rocket project should be graded based the correctness of their similar triangle graph and how well their calculated height matches up with the trigonometric height.

Answer Key: Each group’s Similar Triangle Rocket project will be different, so an answer key would be of no use. Comparing group member’s results against each other could be helpful, since they have the same readings.

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