SCIENCE OF THE SUMMER OLYMPICS: Sarah Robles and the Mechanics of Weightlifting - A Science Perspective (Grades 6-12) Print

Objective:

Framework for K–12 Science Education: PS2.A: Forces and Motion, PS2.B: Types of Interactions, PS2.B: Stability and Instability in Physical Systems, ETS1.A: Defining and Delimiting Engineering Problems, ETS2.B: Influence of Engineering, Technology, and Science on Society and the Natural World


Introduction Notes:

Science of the Summer Olympics

Sarah Robles and the Mechanics of Weightlifting

A Science Perspective (Grades 6-12)

 

Lesson plans produced by the National Science Teachers Association.

Video produced by NBC Learn in collaboration with the National Science Foundation.

 

Background and Planning Information

 

About the Video

Brian Zenowich, a robotics engineer at Barrett Technology, Inc., explains how he and others working in the field of biomimetics use nature to help design and engineer a variety of devices, including some of those used in medicine.  Zenowich discusses and demonstrates his company’s Whole Arm Manipulator, or WAM™ Arm, and compares it to how Olympian weightlifter Sarah Robles’ arms work.  Zenowich also discusses some of the limitations of the robotic arm.

 

0:00     0:12     Series Opening

0:13     0:54     Introducing Sarah Robles

0:55     1:14     Zenowich’s comments on Sarah’s abilities

1:15     1:33     Field of biomimetics

1:34     1:46     Barrett Technology’s WAM™ Arm

1:47     2:03     Comparison of the WAM™ Arm to Sarah’s arms

2:04     2:20     Haptic nature of the WAM™ Arm

2:21     2:32     How biomimetics robots are designed for different uses

2:33     3:07     Sarah’s lifts being filmed with a high-speed camera

3:08     3:31     Zenowich analyzing the lifts

3:32     3:38     Sarah explaining the mechanics of lifting

3:39     4:32     Using the WAM™ Arm to try to mimic Sarah’s movements

4:33     4:42     Constraints of using the WAM™ Arm

4:43     5:02     Sarah explaining technique

5:03     5:22     Summary

5:23     5:35     Closing Credits

 

Language Support

To aid those with limited English proficiency or others who need help focusing on the video, make transcript of the video available. Click the Transcript tab on the side of the video window, then copy and paste into a document for student reference.

 

Connect to Science

Framework for K–12 Science Education  PS2.A: Forces and Motion

                                                                    PS2.B: Types of Interactions

                                                                    PS2.B: Stability and Instability in Physical Systems

 

 

(page 1)

 

 

Related Science Concepts

         Mass

         Forces

         Motion

         Levers

         Fulcrum

         Effort arm

         Resistance arm

         Load

         Mechanical advantage

         Musculoskeletal system

 

Connect to Engineering

Framework for K–12 Science Education

      ETS1.A: Defining and Delimiting Engineering Problems

      ETS2.B: Influence of Engineering, Technology, and Science on Society and the Natural World

 

Engineering in Action

The engineering concepts discussed in Science of the Summer Olympics (SOTSO): Sarah Robles and the Mechanics of Weightlifting include designing and testing robotic devices that mimic structures and motions found in nature, specifically the human arm.  A person’s arm is a third- class lever in which the fulcrum of the lever is the elbow.  The effort arm of the lever is the forearm, which moves as the biceps contract and relax.  The resistance arm of this third-class lever is the weight of the forearm, plus any weight it is trying to move.  Biomimetics engineers use movements like those made by human arms to design and build similar robotic devices.  In the video, Zenowich discusses and demonstrates his company’s Whole Arm Manipulator, or WAM™ Arm, in an effort to better understand how weightlifters like Sarah are able to accomplish amazing feats.  He also talks about the extensive computer modeling needed to test and design materials and configurations within realistic constraints, including the practicality of the device and how it will function in the human environment. This effort involves the engineering knowledge-generating activity experimental engineering research.

 

Take Action with Students

Help students brainstorm to form a list of some of the constraints within which engineers have to work to design devices that mimic the various motions of the human body.  Use the list to initiate a discussion about how robotic body parts cannot truly mimic the motions because of their lack of physiological components, such as muscles and nerves, and an actual brain that sends and receives signals necessary to carry out specific bodily functions. Extend the discussion to include engineering design problems associated with any artificial body parts, or machines that do the function of these parts, including artificial hearts (material failure or rejection), dialysis machines (size), and joint replacements (material failure and fit), among others.

 

(page 2)


 

Inquiry Outline for Teachers

Encourage inquiry using a strategy modeled on the research-based science writing heuristic. Student work will vary in complexity and depth depending on grade level, prior knowledge, and creativity. Use the prompts liberally to encourage thought and discussion. Student Copy Masters begin on page 7.

 

Explore Understanding

Display some common levers or objects that can be used as levers – such as screwdrivers, scissors, brooms, tennis rackets, baseball bats, nutcrackers, tweezers, or nail clippers – and demonstrate how each object might be used.  Also point out some examples of levers that can be found on a playground or around a construction site, including seesaws and wheelbarrows. Use these examples of levers to help students form a definition of a lever: a bar or rod that is free to pivot around a fixed point called a fulcrum. Now use the prompts that follow to spark a discussion of how human legs and arms are levers that can reduce the force needed to move objects over a distance.

         Your arm is a lever because it….

         You use your legs as levers when you….

         If you were lifting a weighted bar from the floor to your chest, you would do it by….

         If you were lifting that same bar from the floor to a position above your head, you would….

         How much mass a weightlifter can lift depends on….

         To prevent injuries while lifting weights, you should….

 

Show the video SOTSO: Sarah Robles and the Mechanics of Weightlifting.

 

Continue the discussion of how arms are levers, and how they are used to move mass, using prompts such as the following:

         When I watched the video, I thought about….

         To lift record-breaking amounts of weight, Sarah….

         The expert in the video claimed that _____ because….

         The WAM™ Arm is like Sarah’s arms in that it….

         The WAM™ Arm is different from Sarah’s arms in that it….

         To complete the snatch, Sarah… until a _____ causes the barbell to….

         To simulate Sarah’s moves, the experts….

         In order to achieve her lifts, Sarah explains that….

 

Before students start their investigations, use diagrams to explain or review the parts of a third- class lever such as the human arm. Then tie this information into what they saw in the video, using the following prompts:

         The body part that provides the force used by Sarah to lift mass is the….

         In terms of levers, the weight is _____ of Sarah’s arm.

         In terms of levers, the effort arm of Sarah’s arm is….

         In terms of levers, the resistance arm of Sarah’s arm is….

 

(page 3)


Ask Beginning Questions

Stimulate small-group discussion with the following prompt: This video makes me think about these questions…. Have groups list questions they have about how a weightlifter makes use of force to lift a certain amount of mass. Ask groups to choose one question and phrase it in such a way as to be researchable and/or testable. The following are some examples.

         How does mass affect the amount of force needed to lift it?

         How does the position of a mass on the resistance arm affect the force needed to lift the mass?

         How does the length of an effort arm affect the amount of force that must be applied to move a mass?

         How does the length of a resistance arm affect the amount of force that must be applied to move a mass?

 

Design Investigations

Choose one of these two options based on your students’ knowledge, creativity, and ability level.

 

Open Choice Approach (Copy Master pages 7-8)

Small groups might join together to agree on one question for which they will explore the answer, or each small group might explore something different.  Students should brainstorm to form a plan they would have to follow to answer the question. Work with students to develop safe procedures that control variables and enable them to make accurate measurements. Encourage students with prompts such as the following:

         The variable I will test is….

         The variables I will control are….

         The steps I will follow are….

         To conduct the investigation safely, I….

 

Focused Approach (Copy Master page 8)

The following exemplifies how students might investigate the question of how the mass of the object being moved by a third-class lever is related to the force needed to move it.

1.      Ask students questions such as the following to spark their thinking:

         What is mass?

         What is force?

         How is mass measured?

         How is force measured?

2.      Students might choose to explore if different masses require different amounts of forces to lift them.  Or, they might choose to explore how the length of a resistance arm affects the amount of force needed to move the same mass.  Give students free rein in determining how they will explore the effect mass on the force needed to lift it.

3.      Ensure that students brainstorm a list of variables and determine which can be controlled and which cannot.  As needed, help them focus on their chosen variable in each trial. Use prompts such as the following:

         The variable I will test is….

         The variables I will control are….

 

(page 4)

 

4.      Students might use different balance masses to test if mass does indeed affect the force needed to move it.  To test this question, students might use a metric ruler (with holes in it), string, masses, and a spring scale to carry out their procedures. One possible procedure might include tying a mass to one of the holes at one end of the ruler, and having one student grip the midpoint of the ruler between the index finger and the thumb loosely enough that it can freely pivot.  The spring scale can be hooked into one of the other holes on the other side of the ruler’s midpoint to determine the amount of force needed to level the ruler. Use prompts such as the following with students:

         The materials I will use are….

         I will measure the force needed to move each mass by….

         I will repeat each trial _____ times for each mass and determine an average force.

         To conduct the investigation safely, I….

5.      Students might continue their investigation by exploring how changing the position of a mass on the resistance arm of their ruler lever might affect the amount of force needed to lift the mass.  Or, they might test if varying the length of the effort arm in their third-class lever affects the amount of force needed to lift a certain mass.

 

Make a Claim Backed by Evidence

As students carry out their investigations, ensure that they record their observations. As needed, suggest ways they might organize their data using tables or graphs. Students should analyze their data and then make one or more claims based on the evidence their data show. Encourage students with this prompt: As evidenced by… I claim… because….

 

An example claim relating mass to the force needed to move it might be the following:

As evidenced bylifting different masses with the same lever, I claim that a larger mass requires more force to lift it than a smaller force does because the values on the spring scale for larger masses were greater than those for smaller masses.

 

Compare Findings

Encourage students to compare their ideas with those of others—such as classmates who investigated the same or similar question, material they found on the Internet, an expert they chose to interview, or their textbooks. Remind students to credit their original sources in their comparisons. Elicit comparisons from students with prompts such as the following:

         My ideas are similar to (or different from) those of the experts in that….

         My ideas are similar to (or different from) those of my classmates in that….

         My ideas are similar to (or different from) those that I found on the Internet in that….

 

Students might make comparisons like the following:

My ideas are similar to my classmates’ in that the data from groups that researched the same question had similar results—mass does affect the amount of force needed to move it.

 

Reflect on Learning

Students should reflect on their understanding, thinking about how their ideas have changed or what they know now that they didn’t before. Encourage reflection, using prompts such as the following:

 

(page 5)

 

 

         My ideas have changed from the beginning of this lesson because of this evidence….

         My ideas changed in the following ways….

         One concept I still do not understand involves….

         One part of the investigation I am most proud of is….

 

Inquiry Assessment

See the rubric included in the student Copy Masters on page 9.

 

 

Incorporate Video into Your Lesson Plan

 

Integrate Video in Instruction

Visualize a Concept:  Use Sarah’s comments at the beginning of the video to dispel the common misconception that “….big muscles [are] going to move a lot of weight.”  Explain that first- and second-class levers can have a significant mechanical advantage – or number of times the lever increases the effort applied to the load.  Explain that a third-class lever like the human arm can increase the distance over which a mass is moved, as well as the speed with which it is moved, but it cannot increase the amount of force needed to move the mass.

 

Compare and Contrast:  Replay the video segment from 0:23 to 0:38 that shows Sarah doing two types of lifts—the snatch and the clean and jerk.  Have students describe how the lifts are similar and different, noting Sarah’s use of her arms and how she positions her body as she goes through each lift.

 

Using the 5E Approach?

If you use a 5E approach to lesson plans, consider incorporating video in these E’s:

Explore:  Use the Focused Approach in the Design Investigations section of the Inquiry Outline to support your lessons on forces and simple machines.

Elaborate:  Use the video to encourage students to learn more about the human musculoskeletal system.  Ask students to research the bones, muscles, and joints involved in a variety of sports, including weightlifting. Have students summarize their findings with detailed diagrams.

 

Connect to … Math

Have students work in pairs to calculate the mechanical advantage (MA) of the levers they used in their investigations. Then have them measure the effort and resistance arms of at least 10 different classmates and calculate those MAs. Challenge students to predict which of their classmates might make a good weightlifter based on the MA of his or her arms.

 

Use Video in Assessment

Ask students to closely watch as you play, perhaps two or three times, the video segment from 2:33 to 3:07, which shows Sarah lifting, and the segment from 3:55 to 4:04, which shows Zenowich attempting to mimic one of her lifts.  Provide students with these instructions:

 

(page 6)

 

 

 

Explain why Zenowich couldn’t complete his lift with a 5-lb mass and a robotic arm, but Sarah could complete hers lifting more than 550 lbs. with her own arms. Use the following terms in your explanation: force, effort, and momentum.

 

 

 

Copy Master: Open Choice Inquiry Guide for Students

 

Science of the Summer Olympics: Sarah Robles and

the Mechanics of Weightlifting

Use this guide to investigate a question about how levers can be used to lift mass. Write your lab report in your science notebook.

 

Ask Beginning Questions

The video makes me think about these questions….

 

Design Investigations

Choose one question. How can you answer it?  Brainstorm with your teammates. Write a procedure that controls variables and makes accurate measurements. Add safety precautions as needed.

         The variable I will test is….

         The variables I will control are….

         The steps I will follow are….

         To conduct the investigation safely, I will….

 

Record Data and Observations

Record your observations. Organize your data in tables or graphs as appropriate.

 

Make a Claim Backed by Evidence

Analyze your data and then make one or more claims based on the evidence your data shows. Make sure that the claim goes beyond summarizing the relationship between the variables.

 

My Evidence

My Claim

My Reason

 

 

 

 

 

 

Compare Findings

Review the video and then discuss your results with classmates who investigated the same or a similar question. Or do research on the Internet or talk with an expert. How do your findings compare?  Be sure to give credit to others when you use their findings in your comparisons.

         My ideas are similar to (or different from) those of the experts in that….

         My ideas are similar to (or different from) those of my classmates in that….

         My ideas are similar to (or different from) those that I found on the Internet in that….

 

Reflect on Learning

Think about what you found out. How does it fit with what you already knew? How does it change what you thought you knew?

(page 7)

 

         My ideas have changed from the beginning of this lesson because of this evidence….

         My ideas changed in the following ways….

         One concept I still do not understand involves….

         One part of the investigation I am most proud of is….

 

 

 

COPY MASTER: Focused Inquiry Guide for Students

 

Science of the Summer Olympics: Sarah Robles and

the Mechanics of Weightlifting

Use this guide to investigate a question about how mass affects the amount of force needed to lift it with a lever. Write your lab report in your science notebook.

 

Ask Beginning Questions

How does the size of a mass affect the amount of force needed to lift it with a lever?

 

Design Investigations

Brainstorm with your teammates about how to answer the question. Write a procedure that controls variables and allows you to make accurate measurements. Add safety precautions as needed. Use these prompts to help you design your investigation.

         I will make a third-class lever by….

         The mass sizes I will use are….

         I will attach the masses to the lever by….

         I will measure force with a _____ by….

         The steps I will follow to test my variable include….

         The variables I will control are….

         I will repeat each trial _____times to make sure….

         To be safe, I need to….

 

Record Data and Observations

Organize your observations and data in tables or graphs as appropriate. The table below is an example using similar balls with different masses moving at the same speed through water.

 

Mass, Force, and Levers

 

 

Force (N) Needed to Lift It With a Third-Class Lever

Mass (g)

Trial 1

Trial 2

Trial 3

Average

__________ grams

 

 

 

 

__________ grams

 

 

 

 

__________ grams

 

 

 

 

  (page 8)

 

 

 

 

 

 

 

 

 

 

 

Copy Master: Assessment Rubric for Inquiry Investigations

 

Criteria

1 point

2 points

3 points

Initial question

Question had a yes/no answer, was off topic, or otherwise was not researchable or testable.

Question was researchable or testable but too broad or not answerable by the chosen investigation.

Question clearly stated, researchable or testable, and showed direct relationship to investigation.

Investigation design

The design of the investigation did not support a response to the initial question.

While the design supported the initial question, the procedure used to collect data (e.g. number of trials, control of variables) was not sufficient.

Variables were clearly identified and controlled as needed with steps and trials that resulted in data that could be used to answer the question.

Variables

Either the dependent or independent variable was not identified.

While the dependent and independent variables were identified, no controls were present.

Variables identified and controlled in a way that results in data that can be analyzed and compared.

Safety procedures

Basic laboratory safety procedures were followed, but practices specific to the activity were not identified.

Some, but not all, of the safety equipment was used and only some safe practices needed for this investigation were followed.

Appropriate safety equipment used and safe practices adhered to.

Observations and Data

Observations were not made or recorded, and data are unreasonable in nature, not recorded, or do not reflect what actually took place during the investigation.

Observations were made, but were not very detailed, or data appear invalid or were not recorded appropriately.

Detailed observations were made and properly recorded and data are plausible and recorded appropriately.

Claim

No claim was made or the claim had no relationship to the evidence used to support it.

Claim was marginally related to evidence from investigation.

Claim was backed by investigative or research evidence.

Findings comparison

Comparison of findings was limited to a description of the initial question.

Comparison of findings was not supported by the data collected.

Comparison of findings included both methodology and data collected by at least one other entity.

Reflection

Student reflection was limited to a description of the procedure used.

Student reflections were not related to the initial question.

Student reflections described at least one impact on thinking.

 

(page 9)

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