how will adding mass to a container affect its...

How Will Adding Mass to aContainer Affect Its Force?

During our unit on forces and motion, we have learned aboutNewton’s First Law. Now you and your partner will conductsome investigations to learn about Newton’s Second Law,using containers and ramps to consider how mass can affectforce.

Your group will have a plastic container to which you can addweights and a ramp with an object at the end that can bepushed by the rolling plastic container. First, hypothesize whatyou will need to do to the container to get the object at thebottom of the ramp to move the farthest. Next, experimentusing the container and weights to see what effect adding massto the container will have in moving the object.

1 of 11How Will Adding Mass to a Container Affect Its Force?

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How Will Adding Mass to a Container Affect Its Force?

Suggested Grade Span

6–8

Task

During our unit on forces and motion, we have learned about Newton’s First Law. Now you andyour partner will conduct some investigations to learn about Newton’s Second Law, usingcontainers and ramps to consider how mass can affect force.

Your group will have a plastic container to which you can add weights and a ramp with anobject at the end that can be pushed by the rolling plastic container. First, hypothesize what youwill need to do to the container to get the object at the bottom of the ramp to move the farthest.Next, experiment using the container and weights to see what effect adding mass to thecontainer will have in moving the object.

Big Idea and Unifying Concept

Cause and effect

Physical Science Concept

Motion and forces

Mathematics Concepts

Data collection, organization and analysisGraphs, tables and representationsMeasurement

Time Required for the Task

Two periods of 45 minutes each.

Context

I used this investigation during a unit on forces and motion. After investigations on Newton’sFirst Law, I began investigations with Newton’s Second Law. Terms such as force and masswere already discussed, and scientific method had been used prior to this lab, so students hadsome knowledge of controls and variables.



What the Task Accomplishes

Students have an opportunity to experience and extend their conceptual understanding ofNewton’s First and Second Laws. Students learn that an object will have more force if it hasmore mass. Students will have the opportunity to practice applying the scientific method –hypothesizing, collecting data and controlling variables.

How the Student Will Investigate

Students work in groups of two or three. Each group has a plastic container (I tried glass once,big mistake) in which they can place weights. I did not have standard weights, but I hadrecycled snowboard grinders which each weighed approximately one to two grams. Each groupalso had a wooden ramp with sides that I had built for my forces and motion unit. Last, eachgroup had an object that would sit at the end of the ramp and be pushed by the rolling plasticcontainer.

I asked the students to hypothesize what they would need to do to the container to get theobject to move the farthest – to give their container the most force. I focused them on the forcethe container would have, and many students suggested other variables, such as friction, thatmight play a role.

Then the students experimented by adding grinders to their containers to see what would pushthat second object the farthest. We discussed how the ramp would need to be set at the samelevel each time so that the only variable to change would be the number of grinders in thecontainer.

Interdisciplinary Links and Extensions

Mathematics/TechnologyStudents can graph results to show patterns as mass increases, or they can compile class datato calculate averages and make predictions about much larger amounts. Students could usecomputers to organize, analyze and interpret data.

Teaching Tips and Guiding Questions

At first, my questions were to guide students in the direction of changing the mass by more thanone or two grinders. I found that students wanted to hover around a certain number, not testingto see whether no weights would make a difference or if the whole container full of weightswould.

I led this investigation with questions such as:

• Have you tried an empty container?• Where is your proof that five weights won’t work?



Although students caught on rapidly that a full container would push the second object farther(thus exhibiting more force), they were reluctant to try to prove their hypotheses wrong.

After students had discovered that more mass caused more force, I led their investigationsfurther (or they led their own) by asking about other ways to increase force. Many students wenton with ways to reduce friction, thus building the speed of their containers and producing moreforce. A guiding tip for this type of investigation is to make sure that the students test only onevariable, and that they keep the same amount of weight while testing other theories.

At the end, I asked whether they could state a rule about the effect of increasing mass on force.This was their conclusion to the investigation.

Concepts to be Assessed

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

Physical Science – Motion and Forces: Students observe and investigate the relationships ofspeed, distance traveled, mass of the object in motion and force. Students observe that anunbalanced force acting on an object changes its speed or path of motion or both and thatgreater mass means greater force. Students need to be able to use the terms force, mass, anddata appropriately.

Scientific Method: Students are able to describe cause-effect relationships with somejustification, using data and prior knowledge. Students observe and explain reactions whenvariables are controlled.

Mathematics: Students collect, organize and analyze data and use graphs, tables andrepresentations appropriately. Students use precise measurements.

Skills to be Developed

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

Scientific Method: Observing, predicting/hypothesizing, collecting/recording/analyzing data,drawing conclusions, communicating findings, challenging misconceptions and raising newquestions.

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 mass onforce.

Physical Science – Transfer and Transformation of Energy: Students observe that forces donot “reside” within objects but are caused by interactions between objects, and that forces (suchas gravity) can act “at a distance” and can cause objects to be pushed or pulled.

Communication: Students use verbal and nonverbal skills to express themselves effectively.

Suggested Materials

I provide plastic containers, cylinders if possible. (Small yogurt containers are okay, althoughcontainers with tops that are the same diameter as the bottoms roll better.) Students will alsoneed a ramp, weights, objects to raise and maintain constant height of the ramp (desks, books),measuring tapes or meter sticks, and an object to be moved by the force. (I used large decks ofcards. They did not tip over.)

Possible Solutions

Students should be able to state a hypothesis, the materials used and the procedures, and theyshould collect and display data. A conclusion, based on data collected, should be stated.

Task-Specific Assessment Notes

NoviceThe student’s solution is incomplete and lacks evidence of conceptual understanding. Thestudent has written an unclear hypothesis and problem statement. There is no evidence of acontrol or of variables. Procedures are unclear, and scientific reasoning is not shown. Somedata have been recorded, but units are not labeled and no conclusions are drawn. Some dataappear to be inaccurately recorded. There is no clear evidence of what the student did to thecontainer that resulted in the second object moving farther.

ApprenticeThe student’s hypothesis reflects understanding of the problem. A diagram is included, but itlacks important labels. Data have been collected, but the presentation of this information is notclear enough to see a pattern. Data may represent the order of the trials made. The proceduresare sketchy at best, and the conclusion is missing.

PractitionerThis student’s solution is complete. The student’s hypothesis reflects prior knowledge (addingmass to the container may cause more force). A labeled diagram is included. An appropriatenumber of trials were conducted, although the data representation does not show a clear



pattern. Sufficient data have been collected and have been used to write a conclusion. Thestudent correctly identifies a relationship between force and mass.

ExpertThis student’s solution is complete and detailed. A clear problem and hypothesis are stated,showing evidence of use of prior knowledge and experience about mass and force. Anappropriate number of trials were conducted. There is evidence of scientific reasoning and howthe student tested the design, controlling variables. Measurements are more precise and dataare displayed showing a pattern of change. Conclusions are supported by data. There isevidence of extended thinking through observations about acceleration and speed as masschanged.



Novice



Apprentice



Practitioner



Expert



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