# BRIDGES, CATAPULTS, AND ROLLER-COASTERS

**INTRODUCTION AND DESIGN CHALLENGE**

The first goal was to introduce the first grade students to the **engineering process: develop ideas, hypothesize, design, build, test and improve**. Special emphasis is put on the improve portion. It is important to teach kids that it is ok to fail and that failure is part of the engineering process. Troubleshooting and figuring out why the project didn't work is one of the fundamental skills in engineering. Once the students were introduced to the engineering process, we started working on projects for the science fair.

**First grade students were challenged to work on three projects:**

**(1) Bridges**: The challenge for this project was to build a beam bridge with a deck and the beams that can stand up and undergo load bearing. Students were divided in two groups of three. One group was given straws and masking tape and the other group was given popsicle sticks and glue. In order to successfully build the beam bridge, students were taught about three physics concepts: **forces, tension and compression**.

**(2) Catapults**: Students were challenged to build a simple catapult that can launch an object into a projectile motion. Students were divided in three groups of two. They were allowed to decide what type of materials they want to use including an object that can store potential energy (something stretchy), an arm for the catapult and a holder for the object to be launched. We covered **potential and kinetic energy** to successfully complete this project.

**(3) Roller coasters**: All students were allowed to build roller coasters by themselves. The only materials used were pipe insulators (cut in half lengthwise to split them open), masking tape and marbles. Students were encouraged to make loops, hills and turns in their roller coasters. The important physics concept for this project was **momentum**. Put an emphasis on how you have to have enough height in order to complete the loop without the marble falling.

**SYLLABUS**

**Week 1**: Talk about what is engineering and what engineers do. Cover the engineering process (develop ideas, hypothesis, design, build, test, improve). Make cut outs of these words and do the exercise with kids where they will glue these words of engineering process in correct order. Show the Bill Nye video of “structures”. Talk about tension (pulling) and compression (pushing).

**Week 2**: Review the tension and compression and explain how in a bridge there is tension on the bottom and compression on the top (demonstrate by a stretchable stick). Show pictures of beam, truss, arch and suspension bridges and point out the differences between each bridge. Specifically, talk about what structures act to hold up the bridge in different types of bridges. Brainstorm ideas on how to build a **beam bridge**. Separate students in groups of two (3 groups of two students each) and provide each group with either one of these combinations of supplies: Popsicle sticks/glue, straws/masking tape, and paper/scotch tape. Have the students draw a design of their bridge on paper. Start building the bridge.

**Week 3**: Continue building the beam bridges (beams need to be strong and big enough to support the entire deck, optimize the number of beams needed for a given deck)

**Week 4**: Test the beam bridges. Ask students to predict how much weight their bridges can bear and where they would be the strongest/weakest. Talk about load bearing for the bridge in comparison to the weight of the bridge itself. Talk about tension/compression. 1st quiz (tension, compression, push and pull force)

**Week 5**: Start to talk about catapults (show pictures and videos of catapults, identify different essential components: arm, holder, stretchable object to build up potential energy). Talk about where energy comes from. What is potential vs kinetic energy? Change of energy from one form into another. Ask to come up with ideas about possible objects that can produce potential energy. Potential vs. kinetic energy video: https://www.youtube.com/watch?v=T5WJoup-RD8.

**Week 6:** Designs for catapults

**Week 7: ** Start building the catapults [(rubber bands, springs for stretchable objects), (spoons, bottle caps for holder), (popsicle sticks, skewers for arm)]

**Week 8**: Finish building the catapults. Introduce roller coasters and show videos about how they work (don’t fall off even while going upside down)

**Week 9**: Start talking about the physics behind roller coasters. Talk about momentum (If you’re riding your bike on a hill, do you have to pedal? No, because you’ve already built enough momentum by the potential energy that was converted to kinetic energy. The built up potential allows you to even go and pass a small hill without pedaling, however, if you have to go climb another hill you will have to start pedaling again). Play the roller coaster game: http://www.funderstanding.com/educators/coaster/

**Week 10**: 2nd quiz (potential energy, kinetic energy and momentum). Design the roller coasters (loops, hills, turns). Start building the roller coasters (out of pipe insulators (cut in half lengthwise), masking tape and use marbles as the ‘cart’).

**Week 11**: Finish building the roller-coasters

**Week 12**: Make the posters for science fair. Include the introduction for the project, physics concepts learned (their definitions), pictures and feedback for the program.

## QUIZZES

Quiz 1: Click here for quiz.

Quiz 2: Click here for quiz.

## THINGS TO CONSIDER FOR FUTURE

Introduce students to engineering design. Change the workflow for the projects.

First, have the students make towers out of blocks so they can understand how a structure stays stable. Then, have the students make the beam bridges out of blocks without using tape and/or glue (Kapla). This way they can truly understand how to strategically arrange the blocks in order to make a stable bridge without resorting to easy solutions like adding more tape).

Then, build the roller coasters (it would be a fun way to see how the tension, compression, energy and momentum plays out together) using the same methods as above. Do not spend more than 2 weeks to introduce the concept and build the roller coasters.

Finally, build the catapults using the same methods as described above.