Materials Included In Kit

Additional Materials Required

Prelab Preparation

For ease of distribution, count out 50 pegs and 50 rubber bands for each student group and place them in a resealable quart-size bag.

Safety Precautions

This laboratory activity is generally considered nonhazardous. Eye protection should be worn in the event of snapping rubber bands and projectile marbles. Marbles that land on the floor should be picked up immediately.

Disposal

All materials may be stored for future use.

Lab Hints

• Enough materials are provided in this kit for 30 students working in groups of three or for 10 groups of students. The introductory activity and the design challenge can be started in one 50-minute class period and the remainder of the design challenge can be modified and tested in a second 50-minute class period. The prelaboratory assignment may be completed before coming to lab, and the questions may be completed the day after the lab.
• This lab may be extended by compiling class data at the end of the challenge. Then a class marble track can be built combining techniques of several groups to see if a prototype can be built that takes longer than any individual group’s prototype.
• Pegboards may vary slightly in the size of the holes. Students may find it necessary to insert and remove pegs using a rubber mallet and pliers while materials are new. With repeated use, the peg holes will widen and it will become easier to insert and remove pegs.

Teacher Tips

• After conclusion of this activity, discuss as a class how the principles used in this activity are applied to design roads on mountains. Propose what would happen if a road went straight down a mountain.

Answers to Prelab Questions

1. Identify the forces acting on the marble as it travels along the track and the effect of each force on the motion of the marble.

   The forces acting on the marble are gravity and friction. Gravity causes the marble to accelerate as it moves along the track, and friction reduces the speed of the marble.

2. In this activity, what is the problem to be solved?

   The problem is getting a marble from the top of the track to the bottom of the track as slowly as possible.

Sample Data

Part I. Introductory Activity—Testing Variables

Part II. Design Challenge

Sketch a copy of the final maze design below. Label the start and the exit.

Answers to Questions

Part II. Design Challenge

1. Did you choose a portrait or landscape orientation for the pegboard? Provide reasoning for your choice.

   We placed the pegboard in the holders in the portrait orientation. This orientation was chosen because this required more turns for the marble to travel to the bottom and the distance of each ramp was shorter allowing less acceleration before another turn.

2. What ideas were part of the original prototype that once tested were found not to work as well as planned?

   The original prototype consisted of a series of bands with very little slope in attempts to create the longest maze possible.

3. What improvements were made to the track design after testing and analyzing results?

   The prototype was modified the most on the second half of the maze. The small slopes worked well at the beginning and the slope of the track was gradually increased as it neared the end. Once the marble was moving faster half way down the track, the track design changed to a steeper slope of the next ramp. Once the marble dropped to the steeper ramp, it rolled upward before descending on to the next ramp, increasing travel time. At the very end of the track a U-shaped design was added to launch the marble back upward before settling in a nearly flat design with twists to slowly complete the maze.

4. What other strategies would you try if you were allowed to use additional materials?

   We would try using thicker rubber bands to increase the surface area between the marble and the track. We would also try coating the marble in glue and then coating it with a coarse material, such as sand, to increase friction.

5. Describe a practical application where the principles used in designing this track could be implemented.

   The same principles used to design this track can be used to design roads on mountains. Often time roads on mountains are a series of hairpin turns making it easier and safer for cars to travel down such a steep decline. Some mountain roads have runaway truck ramps next to the downward road, which are upwardly inclined paths, or roads made of material to increase friction.

References

Special thanks to Arthur Ellis, Bedford Middle School, Westport, CT, for sharing this activity with Flinn Scientific.

Bybee, R.W. “Scientific and Engineering Practices in K–12 Classrooms: Understanding a Framework for K–12 Science Education”; The Science Teacher, Dec 2001, 36–40.

“Engineering Design Process.” Teach Engineering. https://www.teachengineering.org/k12engineering/designprocess#Ask (accessed July 2016).

Introduction

Have you ever moved furniture and thought there had to be an easier way? After moving a few objects, you realize that using a two-wheel hand truck is more efficient to move multiple boxes at once or placing sliding disks under the feet of the couch makes it extremely easy to push it across the room. Whether you realized it or not, you were practicing engineering design!

Concepts

• Engineering design
• Acceleration due to gravity
• Friction

Background

The engineering design process is a series of steps engineers go through to arrive at a solution to a given problem. Engineering design is a cyclical process—meaning that steps are continuously repeated and changes are made until the desired outcome is reached. See Figure 1 for an overview of the engineering design process.

Design criteria are specific requirements that are used to make decisions about what the possible solutions will be and are based on what we want the solution to include. Criteria define the function of the product and its physical design features. Constraints are needs that put limits on the engineer’s design. Some typical constraints are cost, time, and materials that may be used. Good design solutions meet the criteria within the limits defined by the constraints.

The engineering design process begins by asking questions and defining a problem. This step includes determining criteria for a successful solution and identifying constraints. The next step is research to determine possible existing strategies to solve the problem or portions of the problem. Imagining possible solutions or brainstorming as a team allows a collective gathering of any and all options. After all options have been shared, the team selects the option that is logically most likely to solve the problem within the written constraints. The next task involves building a prototype to bring the idea to life! Building the prototype often allows engineers to see if the model is indeed on the path to solving the problem at hand. The prototype is then tested and evaluated. Does it work the way it was intended to work? Where did it work exceptionally well? Where did it fall short? By answering these questions, improvements and design changes can be made so that the prototype more effectively achieves the original goal. The cycle continues until the desired outcome is achieved.

Experiment Overview

The purpose of this activity is to build a marble maze using the materials provided. The lab begins with an introductory activity to explore variables that affect the speed the marble travels on sample tracks. The challenge is to design a marble maze that takes the marble as long as possible to travel from the top to the bottom of the maze without getting stuck or falling off the track.

Materials

Prelab Questions

1. Identify the forces acting on the marble as it travels along the track and the effect of each force on the motion of the marble.
2. In this activity, what is the problem to be solved?

Safety Precautions

The materials used in this activity are generally considered nonhazardous. Safety glasses should be worn as rubber bands may snap off the board if pulled too tightly. If a marble drops on the floor, pick it up immediately. Please follow all laboratory safety guidelines.

Procedure

Part I. Introductory Activity—Testing Variables

A. Rubber Band Placement

1. Place the long side of the pegboard in the two pegboard stands.
2. Place one peg in the upper left hand corner (A1) of the pegboard. Place a second peg in the second row, 3rd column over (C2). Place a third peg in hole N2 (see Figure 2).
   {14071_Procedure_Figure_2}
3. Attach pegs A1 and C2 with a rubber band about half way between the board and the end of the pegs. Wrap excess band around peg A1 so the rubber band is taut between the pegs.
4. Attach a rubber band to pegs C2 and N2 about half way between the board and the end of the pegs.
5. Hold a marble on the rubber band at A1. A partner should be ready to catch the marble if it rolls off the track at N2.
6. Release the marble and observe how it travels along the track. Record your observations on the Marble Down Worksheet.
7. Adjust the rubber band so it is closer to the board and repeat steps 5–6. Note any effect this position has on how the marble travels. 8. Now adjust the rubber band so it is farther away from the board, near the end of the peg. Repeat steps 5–6.

B. Rubber Band Twisting

9. Remove the rubber band from peg N2 and twist it several times. Reattach the twisted band to peg N2.
10. Repeat steps 5–6 from Part A.

C. Speed Bumps

11. Untwist the rubber band between pegs C2 and N2.
12. Add two more pegs at the locations shown in Figure 3, D2 and E2. Note: Make sure the top of the rubber band makes contact with the two pegs.
    {14071_Procedure_Figure_3}
13. Repeat steps 5–6.
14. Add another peg at F2 and repeat step 13.
15. Add another peg at G2 and repeat step 13.

Part II. Design Challenge

The challenge is to design and construct a marble track that takes the marble the longest time to complete. The marble track must meet the following criteria and constraints.

• The track must be constructed of the inclined pegboard, rubber bands and wooden pegs only.
• A maximum of 50 pegs and 50 rubber bands may be used.
• The pegboard must be supported by the wooden stands; it cannot be laid flat on the work surface.
• The pegboard can be oriented in either a portrait or landscape position.
• The marble cannot completely stop moving. If so, the time for that run is disqualified and the marble must be reset at the beginning of the course.
• The timer will start upon the release of the marble and stop as soon as the marble leaves the track, whether that is at the end or before. Any trial in which the marble leaves the track before reaching the end is still considered a complete run.
• Once the design is completed, the marble will be run along the track three times. An average of the three trial times will be taken and the group with the longest time wins!

16. All materials may be saved for future use.

Student Worksheet PDF

14071_Student1.pdf