Grades: 5-8
Author: Sandy Van Natta
Module Description
Participants will observe conversions between potential and kinetic energy, as well as conversions from kinetic energy to heat, as they design and build a roller coaster track for a marble. Using foam insulation tubing, participants will make a track, starting with simple inclines and ending with loops and curves that will carry a marble successfully from start to finish. The only stored energy available for travel will come from the placement of the marble on the top of the initial incline.
Engagement:
Exploration and Elaboration Activities:
Getting Ready:
Engagement
Ask if any participants have ever ridden a roller coaster. Ask those that have ridden what they remember most about the experience. Prompt participants by asking what happens at the beginning of the ride (the cars were initially pulled to the top of the track.)
Remember that at this point there are no wrong answers so treat all responses as having value. Since your participants probably have some background in energy conversion, discussions of potential and kinetic energy may take place here.
Assessment: Encourage all participants to take part in the discussion. The evaluation here is informal.
Exploration
Divide the participants into groups of 4. Ask each group to complete the procedures called for in the Exploration section of the student activity directions and record their observations and data. Some groups may need to work in the hall or another room for enough space for everyone to stretch their track out along the floor.
Since foam tubing may come with a relatively smooth or bumpy inside, participants may need to increase or decrease the starting heights of the incline so that the marble doesn't always roll off the end of the track.
Watch the groups work to be sure that the angle the track slopes down is not so steep that the marble bounces when reaching the level section.
Assessment: Monitor the participants' work and discussions as they work. Ask participants if the points discussed in the Engagement portion of the module support the data they are gathering.
Explanation
The Exploration section provided experience with the idea that gravitational potential energy is proportional to the initial height of the marble above ground. Participants should discover that a marble that starts out twice as high goes approximately twice as far. After discussing the participants' data, point out that the participants could calculate the initial gravitational potential energy of the marble by multiplying the weight of the object (mg, where m is the mass of the object and g is the acceleration due to gravity) times its height above the floor (h). It is this initial energy that is converted into other forms of energy and allows the marble to move along the entire track. Explain that an object can have a large gravitational potential energy because it is high above the ground or has a large weight.
Refer to the explanation in the student activity for more information relating to this module.
Assessment: Monitor the discussion. Ask participants to give examples from their own teaching experiences relating to how they teach energy conversions.
Elaboration
This section gives the participants a chance to apply what they have learned and relax a little. Be sure to have some extra track available for them to build their own roller coasters. As you discuss each group's track and results, make sure that everyone understands that the marble can never rise higher on the track than where it starts because it doesn't have enough energy.
At the end of the activity, revisit participants' experiences on a roller coaster. Ask if participants can explain why the cars have to be pulled to the top of the track. Answers should include the idea that the cars had to be pulled up so that they could then fall due to gravity. (Pulling the cars into position gives them gravitational potential energy that then converts to kinetic energy as the cars move down the track.)
Assessment: Monitor the discussion and make sure everyone is involved. Encourage the participants to make comments and suggestions that might add to or improve the activity.
Teachers need to reinforce important concepts of energy and energy conversions. Completing this activity shows teachers how to accomplish this goal while allowing their students to have a great deal of fun at the same time! Teachers will design a coaster with enough potential energy to allow the marble to complete the designed track. The track will incorporate hills, curves, and loops, while keeping in mind, the total amount of energy originally available as well as energy losses due to friction as the marble moves through the track. Data will be collected and used to support any conclusions drawn from this module.
Content, Technology, and Professional Development:
NSES Content Standard A: Science as Inquiry: As a result of activities, in grades 5-8, all students should develop
NSES Content Standard B: Physical Science: As a result of activities, in grades 5-8, all students should develop an understanding of
NSES PROFESSIONAL DEVELOPMENT STANDARD A: Professional development for teachers of science requires learning essential science content through the perspectives and methods of inquiry.
NSES PROFESSIONAL DEVELOPMENT STANDARD B: Professional development for teachers of science requires integrating knowledge of science, learning, pedagogy, and students; it also requires applying that knowledge to science teaching.
It should take about 2 hours for participants to complete all sections of this activity and discuss the results.
Foam insulation is available at any hardware or building materials store. A scissors or razor blade knife will easily cut the tubing. The tubing is already split on one side lengthwise. By reaching through the existing split with a scissors or knife, the second side can be easily cut.
Foam insulation is available at any hardware or building materials store. A scissors or razor blade knife will easily cut the tubing. The tubing is already split on one side lengthwise. By reaching through the existing split with a scissors or knife, the second side can be easily cut.
Have each group suggest an activity which could be used in their own classrooms to teach energy conversions. Have them write a simple lesson plan for this activity.
The marble gains energy when it is lifted to the top of the track. It stores this energy as gravitational potential energy until it is allowed to roll down the track. Once the marble is in motion, gravity accelerates it downward, and its potential energy is converted into kinetic energy (KE, also called energy of motion). The marble continues to roll until the force of friction stops it. The greater the initial starting height of the marble, the greater the energy stored in the marble, and the farther the marble rolls. The marble stops when all of its KE has been converted to thermal energy due to friction between the marble and the track. In general, doubling the height should more or less double the distance traveled.
When a small hill is placed in the track, the marble loses kinetic energy traveling up the hill but gains gravitational potential energy. As the ball starts back down the hill, the process is reversed. Since the marble gains one type of energy while losing another, the distance traveled should not differ significantly from the distance traveled on a flat track with the same initial height. The marble should be able to travel over hills as long as the hills do not exceed the initial height of the marble and friction between the marble and the track is not too great. Also, hills near the end must be lower than hills near the beginning.
Curves should not make a significant difference in the distance a marble travels. Only if the curve is slanted so that more of the marble makes contact with the bottom and sides of the track will friction increase enough to make a difference in the distance the marble travels.
The same trade-off of potential and kinetic energy discussed with the hill also occurs in a loop. As with hills, if the top of the loop is above the initial starting height, the marble will not have enough kinetic energy to make it to the top of the loop. However, the marble may not go around a loop that is the same height as a hill that it can make it over. With the hill, as long as the marble has any kinetic energy left at the top, it will keep going on over the hill. However, in the case of the loop, a certain minimum speed is required at the top of the loop.
The marble will continue rolling in a straight line until something exerts a force on it. As the marble enters the loop, the track exerts a force on it to make it travel around the loop. The speed and the mass of the marble and the diameter of the loop determine the size of the force the track must exert on the marble to keep it moving in a circular path. As the marble continues moving through the loop, gravity and the force of the track against the marble are combined to make up the centripetal force that keeps the marble moving in a circle. The slower the marble is traveling, the less force the track must exert. If the marble slows down enough that the track doesn't have to exert a force because gravity by itself is enough to provide the centripetal force, the marble will fall.
The marble should be able to traverse loops that are not too high. However, the shape of the loop does affect the result. Loops with gradual curves are more likely to be successful than loops with sharp turns. The location of the loop is important only in that during the trip the marble is gradually losing kinetic energy due to friction. Thus, the farther from the beginning point the loop occurs, the less kinetic energy will be available to be converted into potential energy as the marble goes up the loop. As a result, loops near the end must be lower than loops near the beginning.
Real roller coasters use a shape called a Clothoid loop, which starts out with a large radius and then gradually tightens into a smaller circle. This shape keeps riders from experiencing a very large force when they first enter the loop.
Information from this activity can be used to explain how a toy car moves trough a loop on its track or the energy transformations taking place as a person climbs up and down steps or an object falls toward the ground.
Download Lesson Implementation Template: Word Document or PDF File
Form the groups of participants with diversity in mind. You may want to place participants with weaker physical science backgrounds in groups having participants with stronger backgrounds.
None available for this module.
Taylor, Beverley. Exploring Energy with TOYS, Terrific Science Press, 1998, pgs. 151-161.