Please Note: This is a draft version of the article that appeared in Science & Children, Vol. 33, No.3, Nov./Dec.1995, pp. 12-15. Please refer to the published version if quoting.
  

Crazy Coasters

Marble Roller Coaster Activities Filled With Potential Fun and Energy!

T. Griffith Jones

Science Department Chair

P. K. Yonge Developmental Research School

University of Florida

Linda Cronin Jones

Associate Professor of Science and Environmental Education

Department of Instruction and Curriculum

University of Florida

Energy. This small label identifies what may be the broadest, most sweeping concept in all of the science disciplines. Although we all use the term in life, earth, and physical science classes at virtually every grade level, "energy" remains one of the hardest terms to succinctly define. Even Isaac Newton was unaware of the idea of energy. The very existence of the phenomenon we call energy was still being debated by scientists less than 150 years ago.

Today, energy is a topic common to many scientific, environmental, economic, and even political discussions. Energy in some form impacts nearly every aspect of modern society and applies to every micro and macroscopic physical process occurring in nature. Despite its importance, many elementary teachers devote relatively little time to this major concept, primarily because it is difficult to explain and, in many cases, is difficult for young students to concretely grasp. Energy is a tough concept to illustrate and explain because the only time it can really be seen, felt, or heard is when it is being transferred from one form to another or being transported from one place to another. For us to concretely observe the effects of energy, something has to happen.

Setting the Stage

Imagine your students building a roller coaster with loops to loops, hills, and turns to explore all aspects of energy and motion. Using sections of black foam pipe insulation (3/4 inch inner diameter, thin wall, available at most hardware stores for $0.98 per six-foot section), students can work in small groups to produce incredibly creative roller coaster designs. When split down the middle, the pipe insulation creates two six-foot long flexible roll-ways for a total of 12 feet of track. Sections can easily be formed into loops, corkscrews, curves, S-turns, hills, and valleys.

Student groups can then use other inexpensive materials, such as paper cups, stiff construction paper, cardboard paper towel tubes, and plenty of masking tape to complete their designs. For a grand finale, groups can also be challenged to visibly transfer their marble's kinetic energy to create an event, such as knocking over a stack of paper cups, starting a domino chain reaction, popping a balloon with a pin, or triggering a mousetrap.

Marble roller coasters can be used to either illustrate or help students discover the law of conservation of energy on their own. This fundamental law of physics decrees that energy cannot be created or destroyed; it may only be transformed from one form to another. Students may memorize this law, but direct experiences with marble roller coasters help students truly understand the words in a meaningful way. Many of the experiments and demonstrations frequently used to illustrate this law are boring and irrelevant to students or require expensive apparatus and complicated set-up procedures. Marble roller coasters are a refreshing alternative to these traditional approaches. Even at an introductory level, these crazy coasters allow students to collect good qualitative data on the transfer of potential energy to kinetic energy. For students with more advanced math skills, the activity can be modified to allow for the collection and analysis of more quantitative energy transfer data.

Freedom to Explore

Allowing students to begin their roller coaster experience with an open, exploratory activity produces a flood of positive experiences and attitudes among students. This initial exploration activity will also provide you with a wealth of question topics for further coaster investigations. In the introductory activity, set the stage by telling students they are members of a design engineering team for a new amusement park. To attract huge crowds to the park, they have been asked to design the craziest coaster in their state. But, the design team has one problem. While they have lots of good ideas, they do not have anything concrete to show their boss, who is coming to see them in 40 minutes! To impress their boss, they decide to build a small working model of their design.

Before the activity is scheduled, collect the following set of materials for each group of students: 2 six-foot sections of pipe insulation, masking tape, 2 or more cardboard tubes, 1 piece of poster board or butcher paper, crayons or markers, 1 or more paper cups and 1 small marble. After showing students the materials they have to work with, allow them to work in design teams of three to four. You can leave the design activity completely open-ended or you can require groups to include certain components in their track, such as a loop or a direction change.

Ask each group to think of an exciting or ominous name for their coaster and sketch and label their final designs. If time permits, groups can even make title banners or create advertisement posters to attract potential park guests to the thrills of their coaster.

Give students plenty of working room and their imaginations and enthusiasm will do the rest. The pipe insulation track is so light that one end can be taped directly to a wall or cabinet in order to provide the necessary initial drop height (i.e. maximum potential energy). Our students have found it helpful to push several desks together or put a chair with open back rails on top of a desk to help support the track.

Focus on Problem Solving

During the building and testing process, your students will encounter many small engineering problems, including marbles gaining too much speed and flying off the track, or losing momentum around a turn and stalling. Students can resolve these problems and learn how to improve their designs by observing or trying out out other roller coasters. Leave enough time at the end of class for teams to share and demonstrate their coasters. As students demonstrate their coasters, begin introducing the basic physics concepts underlying the activity. Be careful not to introduce too much content at once. Ask students where the marble gets the initial energy it uses to travel through the coaster. Help students recognize that the marble's energy comes from them exerting (or transferring) their energy of movement to lift the marble up to its starting height at the beginning of the coaster. The work done to actually lift the marble to its starting point is then stored as energy of position or potential energy. The actual amount of potential energy can be measured by calculating the work done to lift it to its beginning height or by multiplying the weight (mass x acceleration due to gravity) of the marble by its height from the ground. The higher or heavier a marble is, the more potential energy it has. A lighter marble can have more potential energy than a heavier marble if it is placed in a higher initial spot.

If coaster designs contain loops, ask students how they were able to get the marble to go around the loop. Most students will report experimenting with the starting track height, or initial potential energy, in order to provide the marble with just the right amount of energy to successfully complete the loop. Other questions you can ask groups include: What was the hardest feature for your team to get right in your design and why?, What would be the most exciting part of your ride for an actual park visitor and why?, and If you had an unlimited budget, explain what you would add to your design to make it the greatest roller coaster in the world.

Determining Actual Potential Energy

Beginning in fourth grade, students can use marbles and their roller coaster track to actually calculate the potential energy of their marbles (see attached activity sheet). Start by asking students how the starting height of their marble affects its energy level. Have students tape several sections of track together to make one long section three to five meters long. Next, have them tape one end of the track higher than the other and bend the track to create two full hills. Have students send marbles down their tracks. If their marbles don't make it over both hills, ask groups to explain why and pose possible design modifications to correct the problem. Once their marbles make it over both hills, have them actually calculate their marble's potential energy.

To calculate the marble's potential energy, students must first determine the weight of their marble. They can either suspend their marble on a spring scale calibrated in Newtons or find the mass of the marble using a pan balance and multiply the mass in kilograms times acceleration due to gravity (9.81 meters/second/second). Second, students must measure the vertical drop their marble experiences (i.e. the distance in meters between the initial starting height and the final height of the track). Finally, to calculate the potential energy of the marble, have students multiply the weight of the marble and the height of the vertical drop. You can have students modify their designs and then calculate the potential energy needed to get the marble close to making it over the first hill and the potential energy needed to get the marble over the first hill but not over the second hill.

For some young students, appropriate units for potential energy can be tricky. In the metric system, potential energy is measured in either newton·meters (also known as joules) or dynes centimeters (also known as ergs). The newton (N), named after Isaac Newton, is the standard unit of force or weight in the metric system. It is defined as the force needed to accelerate a one kilogram mass (2.2 lbs.) one meter per second per second. A dyne is the force needed to accelerate a one gram mass one centimeter per second per second. One Newton of force = 100,000 dynes of force. Elementary students usually find it easier to work with ergs since they are derived from smaller-based gram and centimeter units and thus minimize the amount of metric conversion needed.

Reinforcing Concepts

The main reason students should at least practice determining potential energy is to illustrate the idea that increasing the marble's starting height increases the marble's potential energy. Once students grasp this concept, they should be able to answer the following questions: How does the starting position of the marble affect the speed of the marble at the end of the first hill? (The higher the marble is when it starts, the faster its speed at the end of the hill.) What happens to the marble's energy as it goes up a hill and slows down? (The energy of movement is transformed back into potential energy as it moves up the hill.) Would a marble ever be able to get over a hill higher than its initial starting height? (No.) Why? (A higher hill would require more potentialor kinetic energy than is available.) How would using a different sized marble affect its initial potential energy? (Larger, more massive marbles weigh more and would have more potential energy.) What happens to the marble's potential energy as it moves through the track? (Potential energy is transformed into kinetic energy or energy of motion.) At what point on the coaster does the marble have the greatest potential energy? (At its starting point, when it has the greatest height and is motionless.) At what point on the coaster does the marble have the greatest kinetic energy? (At the end when its height is lowest and its speed is greatest.)

Make sure students realize how the behavior of their marbles reinforce the Law of Conservation of Energy: when marbles roll up a hill they lose kinetic energy and slow down, but at the same time they gain potential energy because they are gaining height. The total amount of energy available doesn't change. Only the form of energy available changes.

Making Science Relevant

Many different science textbooks and other curriculum resource materials now include lessons on roller coasters to illustrate basic energy, force, and motion concepts. In addition, field trips to theme parks with roller coasters are gaining in popularity and availability. Having students build their own coasters serves as a great introduction to a class lesson or field trip focusing on real roller coasters. An in addition to fostering the development of problem solving and cooperative learning skills, Crazy Coaster activities make studying energy and motion fun!

Resources

1. Cronin-Jones, Linda, (1994), The Sunshine State Investi-Gators: Discovering Florida through Problem Solving Activities Grades , Silver Burdett Ginn Publishing Company, Atlanta, GA. Phone: 1-800-848-9500.

2. Hewitt, Paul, (1992). Conceptual Physics-The High School Physics Program, Addison-Wesley Publishing Company, 2725 Sand Hill Road, Menlo Park, CA 94025-9915.

3. Gartell, Jack E, Methods of Motion-An Introduction to Mechanics, Book One, NSTA Publications, 1840 Wilson Boulevard, Arlington, VA 22201-3000. Phone: 1-800-722-NSTA, Catalog #PB039X.

4. Holle, Chris, Quality Education Design Center, Los Angeles Unified School District, 450 North Grand Avenue, Room H-104, Los Angeles, CA 90012.

5. Interactive Physics II (Computer Simulation), Knowledge Revolution, 66 Bovet Road, Suite 200, San Mateo, CA 94402.

6. PRISMS Project, National Diffusion Network, Physics Department, Room 301A, University of Northern Iowa, Cedar Falls, IA 50614

7. Robinson, Paul, (1992), Conceptual Physics Laboratory Manual, Addison-Wesley Publishing Company, Inc., 2725 Sand Hill Road, Menlo Park, CA 94025-9915.

8. Unterman, Nathan (1990), Amusement Park Physics-A Teacher's Guide, J. Weston Walch Publishing Company. Available through NSTA Publications Supplement. Phone: 1-800-722-NSTA, Catalog #OP35IX.

  Marble Roller Coaster Supply Kit and Teacher Activity Guide available through Science Kit & Boreal Laboratories

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