using rubber band energy: what is the relationship...

Using Rubber Band Energy: WhatIs the Relationship Between theNumber of Winds and the Motionand Distance Traveled by aVehicle?

We have been studying aspects of energy and have useddifferent energy sources to make vehicles move – such aswinding a rubber band around the wheel axle of our vehicles.We learned that the rubber band has the potential to move avehicle because of its stored energy.

We have already observed several things about our vehicles:

• No motion will occur unless the stored energy is releasedfrom the wound rubber band.

• When the rubber band is completely unwound, it has nomore stored energy to give the vehicle; however, the vehiclewill continue to roll due to something called "energy ofmotion."

• Friction will slow a vehicle; gravity will help it continue to roll.

For this investigation task, you will be making and testing arubber band vehicle in order to observe how changing thenumber of winds of the rubber band affect the motion and the

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distance traveled. First, make a prediction and identify yourvariables and controls. Then, run 3 trials (for each differentnumber of winds), measure and record distances, and makecareful observations and drawings that help you to drawconclusions. Be sure to link your conclusions to data youcollected.



Using Rubber Band Energy: What Is the RelationshipBetween the Number of Winds and the Motion andDistance Traveled by a Vehicle?

Suggested Grade Span

6–8

Task

We have been studying aspects of energy and have used different energy sources to makevehicles move – such as winding a rubber band around the wheel axle of our vehicles. Welearned that the rubber band has the potential to move a vehicle because of its stored energy.

We have already observed several things about our vehicles:

• No motion will occur unless the stored energy is released from the wound rubber band.• When the rubber band is completely unwound, it has no more stored energy to give the

vehicle; however, the vehicle will continue to roll due to something called "energy ofmotion."

• Friction will slow a vehicle; gravity will help it continue to roll.

For this investigation task, you will be making and testing a rubber band vehicle in order toobserve how changing the number of winds of the rubber band affect the motion and thedistance traveled. First, make a prediction and identify your variables and controls. Then, run 3trials (for each different number of winds), measure and record distances, and make carefulobservations and drawings that help you to draw conclusions. Be sure to link your conclusionsto data you collected.

Big Ideas and Unifying Concepts

Cause and effectChange and constancyDesignForm and functionModels

Physical Science Concepts

Motion and forcesTransfer and transformation of energy



Design Technology Concepts

Design constraints and advantagesInvention

Mathematics Concepts

Data collection, organization and analysisGraphs, tables and representationsMeasurement

Time Required for the Task

One 45-minute class session

Context

This investigation is part of a unit of study on energy and motion. We use a variety of resourcesfor this unit, including adapting some activities from STC’s “Motion and Design” (NationalScience Resources Center/Science and Technology for Children). Prior to conducting thisinvestigation, students built simple vehicles and experimented with and observed how frictionand gravity can affect the speed and distance. (We used K-Nex building pieces to construct ourvehicles. These kits can be purchased as class sets which we share between classrooms.)

Students already have an understanding of terms such as independent and dependent variable,speed, acceleration, forces, gravity, stored energy and kinetic energy. Students have also beenintroduced to our common (used by grades four through eight) lab-report form and havediscussed how to conduct a controlled experiment and a fair test. For this investigation,students were provided with the procedures and a materials list. They had also constructedtheir vehicles prior to this investigation. The focus of this assessment was on makingpredictions using prior knowledge, recording data for multiple trials (for each different number ofwinds) and drawing conclusions that connected their understanding to concepts about energy.

What the Task Accomplishes

This task helps our students to demonstrate learning identified in our state science objectives.Objectives include conducting simple investigations, investigating and explaining how thingswork, following procedures while using appropriate safety precautions, and describing howforces speed up, slow down, stop, and/or change the direction of a moving object. A modelsentence is given on the lab form to help students write a cause-effect prediction, based ontheir prior knowledge. Through careful observations, students will collect and record data in theform of measurements and detailed drawings with supporting descriptions.



The lab-report form includes indicators (written along the left side of the page) to help studentsunderstand what the performance expectations are for each part of the investigation. For thislab, students were not expected to write procedures or list the materials. Procedures weretyped onto the lab form ahead of time, so no scoring is done for that part of the lab. (We havefound that this sometimes saves time when a performance task is given in a 45-minute classperiod. Typically, students in grades six through eight are expected to list their procedures andmaterials when they design their own investigations; however, for this task, we gave them thesame procedures — using two, four, and eight winds of the rubber bands.)

Using the same lab-report form for students in grades four through eight, our teachers can trackstudents’ growth over time. The small box with each indicator allows the teacher to check it,indicating whether that specific evidence is provided. This feedback guides students to improveperformance in future investigations.

How the Student Will Investigate

Students worked in groups of two to four to conduct this investigation. Each individual recordedhis/her own data and observations. Procedures, materials and lab report forms were provided,and students already had constructed their vehicles. (Note: At least one to two additional classperiods would be needed to construct vehicles and to make general observations about usingrubber bands to power them.)

After a brief discussion about the procedures, students were directed to complete the first partof their lab forms: making predictions and identifying variables. Students taped long strips ofadding-machine paper to the floor and marked a starting point at one end. For each trial,students marked their predictions and then the actual distances traveled. These were color-coded for each different number of winds to the rubber bands. For example, for two winds of therubber band, there would be three red dots marking the distance for those three trials. Thishelped students first to see the concept concretely and then to begin to average or generalizehow far the vehicle might typically go with that many winds.

This process was then repeated for four and eight winds of the rubber bands, using other colorsto mark distances. (See student lab forms for procedures in more detail.) Students used metersticks, laid on the floor next to their paper strips, to measure distances in cm. During all trials,students observe carefully, record measurements on the strip of paper and on their data charts,draw and/or make other observations and then determine their conclusions based on datacollected.

Interdisciplinary Links and Extensions

Science/TechnologyStudents could extend this investigation by changing the energy source powering the vehiclesor by making specific observations related to how differing numbers of winds affect accelerationrates. Students could use the questions generated from this investigation for further testing orconduct similar tests on a different surface.



MathematicsStudents could graph results for each trial after calculating the mean, mode and mediandistances for each. Students could compute class averages for the same trials and createscatter plots for the class data.

Teaching Tips and Guiding Questions

It is important to provide some time for students to explore and observe how the rubber-bandvehicles move under different conditions before beginning this assessment task. This providessome prior knowledge for them to base their predictions upon.

Here are some possible questions to ask while they conduct the investigation:

• What have you learned so far that will help you make predictions?• What variables will remain constant? What will you measure?• Are your predictions close to the distances the vehicle traveled? What have you observed

to make you change your predictions for the future trials?• Do you see any patterns in the data you collected?• Where does the energy come from to wind the rubber band? (student’s finger, food eaten,

etc.)• What do your results tell you? What did you learn from your results?• What conclusions can you make based on your results? based on the class results?• What new questions do you have? What further tests could be run?• Have you learned anything that surprised you?

Concepts to be Assessed

(Unifying concepts/big ideas and science concepts to be assessed using the ScienceExemplars Rubric under the criterion: Science Concepts and Related Content)

Physical Science – Motion and Forces; Transfer and Transformation of Energy: Studentsobserve and investigate the relationships of speed and distance traveled when different forcesare applied. Students observe than an unbalanced force acting on an object changes its speedor path of motion or both. Students understand that as stored energy increases, so does theinitial speed acquired by the vehicle, and that the faster a vehicle moves, the more energy ofmotion it has.

Design Technology – Invention: Students learn that several steps are involved in makingthings. Students create a model that will provide reliable data and information for designmodifications.



Design Technology – Design Constraints and Advantages: Students see that somematerials are better than others, depending on the task and characteristics of the materials.Students recognize constraints in the materials and methods used and that materials anddesigns need to be accurately described in order to be re-created by someone, using thewritten description.

Scientific Method: Students determine the patterns and/or which kinds of change arehappening by making a table of measurements. (For example: How does the number of windsaffect the speed and distance of the vehicle?) Students observe and explain reactions whenvariables are controlled. (For example: What effect does the number of winds have on thespeed and distance of the vehicle?) Students observe how the design alters the function of thevehicle (form and function). Students see that how a model works after changes are made to itmay suggest how the real thing would work if the same thing were done to it, and that choosinga useful model (not too simple/not too complex) to explore concepts encourages insightful andcreative thinking in science, mathematics and engineering (models).

Mathematics: Students represent and analyze data appropriately, identify trends and patternsand use tables to show how values of one variable are related (increase, decrease, etc.) tovalues of another. Numerical data and precise measurements are used in describing events,answering questions, providing evidence for scientific explanations and challengingmisconceptions.

Skills to be Developed

(Science process skills to be assessed using the Science Exemplars Rubric under the criteria:Scientific Procedures and Reasoning Strategies, and Scientific Communication Using Data)

Scientific Method: Using prior knowledge, predicting/hypothesizing, manipulating tools,observing, collecting/recording/analyzing data, drawing conclusions, making connections,communicating findings, challenging misconceptions and raising new questions.

Other Science Standards and Concepts Addressed

Scientific Method: Students describe, predict, investigate and explain phenomena. Studentscontrol variables.

Scientific Theory: Students look for evidence that explains why things happen and modifyexplanations when new observations are made.

Physical Science – Motion and Forces: Students observe and record the effects of differentamounts of force on speed and distance.

Physical Science – Transfer and Transformation of Energy: Students observe that forces donot “reside” within objects but are caused by interactions between objects. Students observethat energy can be stored released and/or transferred to another object. Students understand



that energy is a property of many substances and is associated with heat, light, electricity,mechanical motion, sound, nuclei and the nature of a chemical. Students observe that energy istransferred in many ways and that forces such as gravity can act “at a distance” and can causeobjects to be pushed or pulled.

The Designed World: Students observe that tools extend the ability of people (to make things,to move things, to shape materials) and that manufacturing requires a series of steps and,depending on the task, careful choice of materials (based on their characteristics).

Suggested Materials

Groups of two to four students will each need:

• Adding-machine tape or long strips of paper (about 10 meters)• Three colors of markers (red, blue, green) or stick-on dots• Tape• Pencil• Vehicle (made of K-Nex building pieces) with several (three) rubber bands• Meter sticks or measuring tapes• Safety goggles

Lab-report forms are completed by each individual student. Teachers may want to make anoverhead transparency of the class data table for postinvestigation discussions.

Possible Solutions

The model sentence on the lab form should help students write a cause-effect prediction, basedon prior knowledge. Scientific terminology should be used appropriately (e.g., energy,potential/stored, kinetic, mass, etc.) throughout the investigation. Independent (number of timesI wind the rubber band) and dependent (distance the car will travel) variables and constants(mass, weight, design of car, number of rubber bands, direction and manner that rubber bandsare wound each time, etc.) should be identified.

Students must conduct and collect data for three trials for each number of winds, according toprocedures given (a total of nine trials). For this lab, students were not expected to writeprocedures or list materials. Observations should be recorded in the form of detailed drawingswith supporting descriptions. Drawings of lab setups should have labels for important words.Units of measure (cm) should be included and appear to be accurate. “Selected distance”should be an average, based on actual trials, and/or show reasoning why if an average was notused.

Note: Class data vary because these student work samples came from different classrooms.Some teachers did not require all data to be filled in – only for the class averages.



Task-Specific Assessment Notes

NoviceThis student completes the task, but the solution is lacking in details and conceptualunderstanding. The student’s reason, “builds more energy,” shows an understanding thatwrapping the rubber band is related to creating more energy for the car. The hypothesis showssome evidence of understanding but does not give a clear “if-then” statement. The reader is notsure what “it” refers to (“if you wrap it ...”). The student identifies what will be measured(“distance”) but not the units to be used. The student incorrectly states that the independentvariable is “times you turn the axel” instead of times the rubber band is wound. Some constantsare correctly identified. A drawing of the setup is included but has no labels. The data tableincludes all trials but does not include units of measure and isdifficult to read. The accuracy of the data is questionable, since it seems to vary so greatly forthe same number of winds. Observations are limited in details and do not relate to the questionbeing tested. The student’s conclusions make a link to the hypothesis, but the student does notrefer to data collected. Although science terms are used in stating a Big Idea, there is noevidence of conceptual understanding in the student’s response. There is an attempt to raise anew question for further exploration, but it is not written as a question (“more weight”).

ApprenticeThis student completes the task, but the solution shows limited conceptual understanding. Thehypothesis has a clear “if-then” statement, but the reasoning seems fuzzy. The studentidentifies what will be measured (“distance the car travels”) but not the units to be used. Thestudent states the independent variable as “tension” — which is related to, but not the same as,the times the rubber band is wound. Some constants are correctly identified. A drawing of thesetup is included but does not include important information and only has labels for the people.The data table is missing one of the trials and does not include units of measure. One of theaverages given is accurate. One observation is made but is limited in details, making it unclearexactly what is being compared. The student’s data are summarized but not specific.Conclusions make a link to the hypothesis, but the student does not refer to data collected.Although some science terms are used in stating what was learned, there is no evidence ofconceptual understanding in the student’s response. There is an attempt to raise a newquestion for further exploration but it is still vague as to what the student would actually test.

PractitionerThe solution is complete and all necessary parts of the lab report are present. The hypothesishas a clear “if-then” statement, and the reasoning relates to forces and motion concepts. Thestudent identifies what will be measured (“distance the car moves”) but not the units to be used.The student accurately states the independent variable as the times the rubber band is woundaround the axle. Constants are correctly identified. A labeled drawing of the setup is included.The data table is complete and accurate and includes units of measure. Three relatedobservations are made that compare the data being collected. Conclusions make links to thehypothesis and to data collected. Science terms "potential energy" are used correctly in statingwhat was learned and how the investigation relates to the concept. A new question is raised for



further exploration and extends this investigation. The “new” question builds upon the lastquestion tested.

ExpertThis student’s solution is complete and detailed. The hypothesis has a clear “if-then” statement,and the reasoning relates to forces and motion concepts. All independent and dependentvariables and controls are identified. Units to be used are included. A labeled drawing of thesetup is included. The data table is complete and accurate and includes units of measure. Theobservations made give some details and compare the data being collected to other groups’findings. Conclusions are supported by data and link to the hypothesis. There is evidence ofconceptual understanding and extended thinking in the discussion of sources of error andfurther questions to test.



Novice



Apprentice



Practitioner



Expert



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