MnSTEP Teaching Activity Collection > MnSTEP Activities > Investigating Projectile Motion: Creating a Catapult

Investigating Projectile Motion: Creating a Catapult

Abigail M. Baker, Benilde-St. Margaret's School, St. Louis Park, MN
Based on an activity created by BSM Physical Science teachers and a lesson posted by Trish Loeblein at the PhET Interactive Simulations web site
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This lesson is for 9th grade physical science students. It begins with an inquiry-based lesson using a projectile motion computer simulation. It culminates with students building a catapult; applying and connecting science knowledge from previous units; and preparing an extensive lab report—the portfolio.

Learning Goals

This activity is designed for students to
1. Conduct research of catapults to help refine brainstorm design.
2. Create a catapult that will toss a projectile onto a target 3 m away using a minimum of 9 supplies from a given list.
3. Practice calculating kinetic and gravitational potential energy.
4. Observe the relationship between gravitational potential energy, elastic potential energy, and kinetic energy.
5. Use Newton's Laws to explain the motion of a projectile.

Key Concepts
1. Scientific Methods
2. Newton's Laws
3. Forces
4. Friction
5. Energy Transformations (elastic potential, gravitational potential, kinetic)
6. Conservation of Energy

Vocabulary Words
- gravitational/elastic potential energy
- elastic potential energy
- kinetic energy

Context for Use

This project is used with 9th graders in Physical Science working in groups of 2-3, who are just finishing the Energy unit. They need to work within a set of guidelines while thinking out of the box for catapult construction. Students are given one month for the entire catapult part—including research, brainstorm, and execution.

Subject: Physics:Classical Mechanics:Projectile Motion
Resource Type: Activities:Lab Activity
Grade Level: High School (9-12)

Description and Teaching Materials

1. Use the PhET Projectile Motion simulation to discuss projectile motion qualitatively with students (See link below for a sample lesson to use with the simulation.)
2. Have students build a catapult (See handout attachment.) Catapult project description (Acrobat (PDF) 100kB Aug14 09)

Teaching Notes and Tips

Most of the supplies are common household items. Some of the items can be from recycled materials—Popsicle sticks, rubber bands (from green onions, etc.), and cardboard. Students will also trade materials with each other. After doing this and other projects throughout the years, we've developed a "trade bin" with commonly used materials.

This project has been used as a review of energy transformations for several years. The only thing not previously done is the use of the PhET simulation before catapult construction.

Online research for building a catapult is encouraged (as a problem solving method). Students end up having to modify what they find because kits for purchase or online instructions don't include the required materials.

The portfolio is a more extensive lab report including group parts and individual parts.

1. Lab Safety is always reinforced
2. Practice courses are set up so students who finish building earlier can try their catapults out.
3. Official launches on a specific day are the only ones that count.
4. Besides best catapult performance awards, I also give out awards such as "most original design," "best use of recycled materials," "best team spirit."

Helpful websites:
PhET Projectile Motion Simulation

A Projectile Motion-Introduction (Inquiry Based) Lesson by Trish Loeblein


Ongoing Assessment
- Work Ethic during in-class work days

Written Assessment
- Lab Report Portfolio including Catapult research

Lab Execution Assessment
- Catapult Construction:
o Is the catapult made of the proper requirements?
- Catapult Performance: follows all guidelines


9-12.I.B.1. Experimental Design
9-12.I.B.2. Qualitative/Quantitative Data
9-12.I.B.3. Math to analyze data/Models to support conclusions
9-12.I.C.5. science/technology influenced by social needs
9-12.I.D.1. Trace the development of scientific invention and impact on society
9-12.I.D.2. Examples of scientific advancements by other civilizations/cultures
9-12.II.C.1, 2 Potential energy, KE conversion to PE, PE conversion to KE
9-12.II.D.1. Newton's Laws
9-12.II.D.2. Friction and Gravity effects on motion
9-12.II.E. Forces

References and Resources