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+ Reinventing Introductory Physics for Life Scientists Edward F. Redish Department of Physics University of Maryland

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Page 1: Reinventing Introductory Physics for Life Scientists - PBworksumdberg.pbworks.com/w/file/fetch/87603985/UBC.pdf · Reinventing Introductory Physics for Life Scientists Edward F. Redish

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Reinventing Introductory Physics for Life Scientists

Edward F. Redish Department of Physics University of Maryland

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+Teaching physics

for life science students: The changing landscape

10/16/14 University of British Columbia 2

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+Teaching physics for life science students is one of the main things physics departments do

  The University of Maryland Physics Department now teach almost as many biology students as we do engineers and the numbers are growing.

  They are one of our primary constituents.

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+What do we teach our life science students?   The typical algebra-based physics class

traditionally taken by biologists is just calculus-based physics “cut down” by reducing the level of math required.

  It looks very much like a remedial course for a mechanical engineer who is taking a catch-up class in math at the same time.

  Often it was seen as a “weed-out” course for pre-meds.

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+The new biology

  Biology has been changing fast.

  New probes, methods, and models are enabling a dramatically increased understanding of the mechanisms of life at all scales from the molecular to the ecological.

  Quantitative measurements and modeling are emerging as key tools for discovery

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+Biologists want an upgrade

  Leading research biologists and medical professionals have increasingly been calling for a major reform of undergraduate instruction.

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2003 2009

2011

2013

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+This is an interesting challenge. Can we do it?

  These reports have specific requests. They want courses that   Stress scientific skills / competencies (and they have identified many fairly specific ones)   Include topics essential and relevant for modern biology.   Enhance interdisciplinarity.

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10/16/14 University of British Columbia

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+In the summer of 2010, HHMI offered an opportunity to four universities:

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Create a proposal to develop prototype materials for biologists and pre-meds with a focus on scientific competency building and interdisciplinary links in

  Chemistry (Purdue)   Math (UMBC)   Physics (UMCP)   Capstone case study course (U of Miami)

10/16/14 University of British Columbia

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+Goals of NEXUS: A national demonstration project   Create prototype materials

  An inventory of open-source instructional modules that can be shared nationally .

  Interdisciplinary   Coordinate instruction in biology, chemistry, physics, and math.

  Competency based   Teach generalized scientific skills so that it supports instruction in the other disciplines.

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10/16/14 University of British Columbia

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+Competencies (SFFP)   E1 Apply quantitative reasoning and appropriate

mathematics to describe or explain phenomena in the natural world.

  E2 Demonstrate understanding of the process of scientific inquiry, and explain how scientific knowledge is discovered and validated.

  E3 Demonstrate knowledge of basic physical principles and their applications to the understanding of living systems.

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  E4 Demonstrate knowledge of basic principles of chemistry and some of their applications to the understanding of living systems.

  E5 Demonstrate knowledge of how biomolecules contribute to the structure and function of cells.

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NEXUS/Physics: Overview

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+The NEXUS Development Team (UMCP)

  Physicists   Joe Redish   Wolfgang Losert**   Chandra Turpen   Vashti Sawtelle   Ben Dreyfus*   Ben Geller*   Kimberly Moore*   John Gianini* **   Arnaldo Vaz (Br.)

  Biologists   Todd Cooke   Karen Carleton   Joelle Presson   Kaci Thompson

  Education (Bio)   Julia Svoboda   Gili Marbach-Ad   Kristi Hall-Berk*

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10/16/14 University of British Columbia * Graduate student ** Biophysicist

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+Discussants: UMCP co-conspirators   Physicists

  Arpita Upadhyaya**   Michael Fisher   Alex Morozov**   Peter Shawhan

  Biologists   Marco Colombini**   Jeff Jensen   Richard Payne   Patty Shields   Sergei Sukharev**

  Chemists   Jason Kahn   Lee Friedman   Bonnie Dixon

  Education   Andy Elby (Phys)   Dan Levin (Bio)   Jen Richards (Chem)

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10/16/14 University of British Columbia ** Biophysicist

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+Off-campus collaborators   Physicists

  Catherine Crouch* (Swarthmore)

  Royce Zia* (Virginia Tech/Iowa State)

  Mark Reeves (George Washington)

  Lilly Cui & Eric Anderson (UMBC)

  Dawn Meredith (U. New Hampshire)

  Steve Durbin (Purdue)

 Biologists   Mike Klymkowsky*

(U. Colorado)

 Chemists   Chris Bauer*

(U. New Hampshire)   Melanie Cooper*

(MSU)

 Education   Janet Coffey

(Moore Foundation)   Jessica Watkins

(Tufts University)

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*NSF TUES project 10/16/14 University of British Columbia

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University of British Columbia Extensive negotiation among the physicists and the biologists

Reinventing physics for life science students

One instructor for a pilot section of 20 students

Two instructors run 2 pilot sections of 10-15 students

Six instructors run 6 different sections ~100 students each

The NEXUS teams has been iteratively re-designing the introductory physics sequence required for all life science majors.

Significant shifts in topics & Significant shifts in pedagogy

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+Reconstructing Physics for Life Scientists – from the ground up

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+ Changing the culture of the course

  We seek content and examples that have authentic value for biology students.   We want upper division bio to make physics a pre-requisite.

  We do not assume this is a first college science course.   Biology, chemistry, and calculus are pre-requisites.

  We do not assume students will have later physics courses that will “make things more realistic.”   The value added by physics can’t wait until later classes.

  We choose different content from the traditional class.   Atomic and molecular examples   Chemical energy   Motion in fluids   Random motion and its implications

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+The pedagogy   The class is structured to use

what has been learned about pedagogy from DBER.

  Enable active learning and “flipping”   Wiki-book with short on-line readings.   Clicker questions   “Thinking problems” for HW emphasizing

sense making and coherence   Groupwork activities

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Redish & Hammer, Am. J. Phys., 77 (2009) 629-642.

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+Starting in a hard place as to physics for biology students   It turns out there are significant

cultural differences between how biologists and physicists view this course.

  Many biologists saw most of the traditional introductory physics class as useless and irrelevant to biology – and the physicists claim that “we can apply physics to biology examples” as trivial and uninteresting.

  Physicists saw a coherent structure with no room for change.

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+After many interesting and illuminating discussions   We came to a better understanding

of what it was the biologists needed and how the disciplines perceived the world and their science differently.

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10/16/14 University of British Columbia

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+And...   We continue to negotiate these changes

through extensive discussions among biologists, chemists, and physicists.

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But...   We (try to) maintain the crucial components

of “thinking like a physicist” – quantification, mathematical modeling, mechanism, multiple representations and coherence (among others).

10/16/14 University of British Columbia

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+Disciplinary expectations   There is much more than changing

the table of contents and the prerequisites.

  From students’ experience with a discipline they bring expectations about the knowledge they are learning that tell them what to pay attention to in the context of activities in a science class.

  These expectations frame the activities for the students and affects how they interpret what they are learning.

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10/16/14 University of British Columbia Hammer, Elby, Scherr, & Redish, in Transfer of Learning: Research and Perspectives, J. Mestre, ed. (Inf. Age. Pub, 2004) .

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+Physics   Introductory physics classes often stress

reasoning from a few fundamental (often mathematically formulated) principles.

  Physicists often stress building a complete understanding of the simplest possible (often abstract) examples (“toy models”) – and don’t go beyond them at the introductory level.

  Physicists quantify their view of the physical world, model with math, and think with equations.

  Physicists concern themselves with constraints that hold no matter what the internal details. (conservation laws, center of mass, ...)

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10/16/14 University of British Columbia

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+Biology   Biology is highly complex and is often emergent,

including the property of life itself.   Most introductory biology does not emphasize

quantitative reasoning or problem solving.   Much of introductory biology is descriptive

(and introduces a large vocabulary).   Biology contains a critical historical constraint: natural

selection can only act on pre-existing molecules, cells, and organisms for generating new solutions.

  Biologists (both professionals and students) focus on and value real examples and structure-function relationships.

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+What can physics do for biology students?

  Put “legs under” complex topics introduced in bio and chem through the use of “toy models.”   Fluids   Chemical reactions   Thermodynamics and statistical physics

  Help develop scientific skills that may be harder to build in intro chem and bio because of the complexity of the examples.   Blending math with physical sense making   Thinking and reasoning with equations.   Quantifying experience

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+Some solutions: New content, new approaches

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+ The Debates: Inclined Plane/Projectiles

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  Pro: Our physicists saw these topics as crucial for learning how to use vectors, a general and powerful tool.

  Con: Our biologists saw the inclined plane and projectiles as typical physics hyper-simplification with little or no value.

  The resolution: We replaced these topics with examples from biological motion and moved electric forces to the first term to provide serious vector examples.

10/16/14 University of British Columbia

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+The Debates: Force / Energy

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  Pro: Our biologists saw the emphasis on forces as superfluous and asked to do everything in terms of energy.

  Con: Our physicists considered forces as “privileged” – essential for the fundamental concepts of motion.

  The resolution: We reframed the treatment of forces as “The Newtonian Framework” – analogous to “The Evolutionary Framework” in biology; something that sets the language and ontology – what you look for.   This clarified what was a model of a specific system and what was

a part of a more general framework.   More effort was devoted to energy and a bit less to forces.

10/16/14 University of British Columbia

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+Revising the content   Expand

  Atomic and molecular models of matter

  Energy, including chemical energy

  Fluids, including fluids in motion and solutions

  Dissipative forces (drag & viscosity)

  Diffusion and gradient driven flows

  Kinetic theory, implications of random motion, statistical picture of thermodynamics

  Reduce substantially or eliminate entirely

  Projectile motion   Universal gravitation   Inclined planes, mechanical

advantage   Linear momentum   Rotational motion   Torque, statics, and angular

momentum   Magnetism   Relativity

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10/16/14 University of British Columbia

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+Revising the approach

  Be explicit about modeling and analyzing as systems.

  Emphasize equations as guides to thinking and reasoning

  Focus on coherent vs. random motion

  Develop quantification skills and a sense of scale

  Use modern pedagogical tools

  Give problems where building equations are the point

  Do problems with simulations, video, numerical calculations (solving ODEs on a spreadsheet)

  Do multiple labs on random motion

  Give estimation problems on macro & micro scales

  Create clicker and groupwork problems

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We want to So we

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+New content: Fun new physics

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+Example 1: Random vs. coherent motion

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This 'Water Channels in Cell Membranes' movie was made with VMD and is owned by the Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, at the Beckman Institute, UIUC

Ohkubo & Tajkhorshid, Structure (Cell Press), 16:1 (2008) 72-81. (Department of Biochemistry, Beckman Institute and Center for Biophysics and Computational Biology, UIUC)

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+Goals for the laboratories   Labs should be well integrated

with other parts of the class – and biologically authentic.

  Develop student research skills:   Use modern technology and tools   Focus on sensemaking (data thick)   Focus on experimental design (protocol thin)   Focus on the value of quantification

  Foster interdisciplinary transfer   Explore biologically relevant experiments   Help students consider: “What biology do you

learn from a physical measurement?” 10/16/14 University of British Columbia

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+ Random vs coherent motion

  In the rest of the class, students have learned that   For random motion   For coherent motion

  They take data in physical situations (tipped microscope stage with different sized microspheres) and do log-log plots of the data, identifying the slope to determine the type of motion.

  They apply this insight to the motion of tubules within an onion skin cell to determine whether the cell is alive or dead.

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Δr( )2 = 6Dt

Δr( )2 = v0t( )2

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+Observing random motion in the lab

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+ Inside an onion skin cell

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+Example 2: Chemical bonding   In intro chem and bio classes,

students learn about chemical reactions and the critical role of energy made available by molecular rearrangements.

  But students learn things by rote that feel contradictory to them and they often don’t know how to reconcile. 1.  It takes energy to break a chemical bond. 2.  Breaking the bond in ATP is the “energy

currency” of cellular metabolism. 10/16/14 University of British Columbia

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W. C. Galley, J. Chem. Ed., 81:4 (2004) 523-525.

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+Many students infer a “piñata” model of a chemical bond.

"But like the way that I was thinking of it, I don't know why, but whenever chemistry taught us like exothermic, endothermic, like what she said, I always imagined like the breaking of the bonds has like these little [energy] molecules that float out, but like I know it’s wrong. But that's just how I pictured it from the beginning."

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+How physics can help   Build a coherent story using toy models

  Bulldog on a skateboard

  Atomic interactions and binding

  Reactions in which bonds are first broken and then stronger ones formed (the Gauss gun)

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+ A series of clicker questions (PhET based) helps students get comfortable with negative PE and with the concept of binding energy.

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Same problems analyzed with shifted zero of PE – one positive E, one bound.

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+Bound states HW problem

The skateboarder is just an analogy for the cases we are interested in -- interacting atoms.

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If the atoms have an energy of -7.5 units as shown by the solid line in the figure, would you have to put in energy to separate the atoms or by separating them would you gain energy? How much? Explain why you think so.

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+The Gauss Gun: A classical analog of an exothermic reaction

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+Student drawing from a HW on the reaction H2 + O2 2H2O

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+Final exam (MC) The figure at the right depicts a situation in a chemical reaction complex . We model the combined system as consisting of three parts, shown red, green, and blue. Each part can be pulled away from the remaining pair or vibrate against them. Two potential energy curves are shown: one in blue that shows what happens to the potential energy as the blue part is pulled away from the red-green pair, one in red that shows what happens to the potential energy as the red part is pulled away from the blue-green pair.

6.2 (5 pts) Which part takes less energy to break off from the molecule, blue or red?

a. The blue part. b. The red part. c. They will each take the same energy to remove. d. You can’t tell from the information given.

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5% 95%

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+Some lessons to be learned: Teach physics standing on your head

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+Teaching the trial class under the microscope   We taught the first two years of

NEXUS/Physics in small (N~20) flipped classes with lots of interaction.

  We often asked students what they had learned in bio and chem classes.

  We videotaped all classes and interviewed many students throughout the class.

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+We learned some lessons (some painful)   Bio students were much more interested

and willing to engage with the physics when they saw its relevance for their other classes.

  Bio students appear much more capable when discussing issues in bio and chem (especially when we stopped evaluating them primarily on mathematical fluency).

  We learned of many inconsistencies, sloppy presentations, and unstated (often unreasonable) assumptions in our traditional physics approaches to teaching.

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+Example 3   If two uniform sheets of equal and

opposite charge can be treated as if they were infinitely large, which of the following graphs might serve as a graph of the electrostatic potential as a function of the coordinate x along the dotted line?

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+About half the students gave a “correct” answer (3 or 9), but...

  Two students objected.   One argued any curve should have “spikes” as you passed through the plate, since you would surely get close to an ion.   A second argued that the potential curve had to be zero along the center of the plates since for whatever charge you found contributing to the potential on one plate, there would be a matching and opposite one an equal distance away on the second plate.

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+ My example was undermining core epistemological lessons I was trying to teach.   Physics is about something real.

Whenever you think about a physics example, start from a mental image of a physical situation and refer everything back to it.

  In physics we often use simple models to illuminate core ideas. Be explicit about your assumptions – what you are paying attention to and what you are ignoring.

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+The more we listened the more we learned

  Students took on a more integral role in establishing the class as a learning community.

  Students provided the bio and chem expertise needed – faculty didn’t need to know it!

  We learned new perspectives on what we were teaching – both on traditional and new material.

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+A deeper problem

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  An epistemological analysis* can help us both understand the problems in student-faculty communication and in helping us design more effective instructional environments.   * What do we use to decide that we know something?   * How do we approach the building of new knowledge?

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+Example 4: The “go-to” epistemological resource

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  The epistemological stances naturally taken by physics instructors and biology students may be dramatically different – even in the context of a physics class.

  One example from my observations of other faculty teaching NEXUS/Physics yields an insight.

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+Epistemological resources

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Knowledgeconstructed

from experience and perception (p-prims)

is trustworthy

Algorithmic computational steps lead to a trustable

result

Information from an authoritative

source can be trusted

A mathematical symbolic representation faithfully

characterizes some feature of the physical or geometric

system it is intended to represent.

Mathematics and mathematical manipulations

have a regularityand reliability and are

consistent across different situations.

Highly simplified examples can yield

insight into complex mathematical

representations

IntroPhysicscontext

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+Epistemological resources (short names)

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Knowledgeconstructed

from experience and perception (p-prims)

is trustworthy

Algorithmic computational steps lead to a trustable

result

Information from an authoritative

source can be trusted

A mathematical symbolic representation faithfully

characterizes some feature of the physical or geometric

system it is intended to represent.

Mathematics and mathematical manipulations

have a regularityand reliability and are

consistent across different situations.

Highly simplified examples can yield

insight into complex mathematical

representations

Physical intuition (experience & perception)

Calculationcan be trusted

By trusted authority

Physical mapping to math

(Thinking with math)

Mathematical consistency

(If the math is the same, the analogy is good.)

Value of toy models

IntroPhysicscontext

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+

The figure shows the PE of two interacting atoms as a function of their relative separation. Is the force between the atoms at the separation marked C

  attractive ?   repulsive?   zero?

C

B A Total energy

r

Potential Energy

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+On a piece of paper

Sketch out a brief argument how you would explain this result to your students in an introductory physics class.

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C

B A Total energy

r

Potential Energy

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+ How two different professors explained when students got stuck.

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  Remember! (or here)

  At C, the slope of the U graph is positive.

  Therefore the force is negative – to smaller r.

  So the potential represents an attractive force when the atoms are at separation C.

F = −∇U F = − dU

dr

This figure was not actually drawn on the board by either instructor.

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+ Wandering around the class while the students were considering the problem I found a different approach produced a better response.

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  Think about it as if it were a ball on a hill. Which way would it roll? Why?

  What’s the slope at that point?

  What’s the force?

  How does this relate to the equation

F = − dU

dr

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+I conjecture that a conflict between the epistemological stances of instructor and student make things more difficult.

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Calculationcan be trusted

By trusted authority

Physical mapping

to math(Thinking with math)

Physics instructors seem more comfortable beginning with familiar equations – which we use not only to calculate with, but to code and remind us of conceptual knowledge.

Physical intuition (experience & perception)

Physical mapping to math

(Thinking with math)

Mathematical consistency

(If the math is the same, the analogy is good.)

Most biology students lack the experience blending math and conceptual knowledge, so they are more comfortable beginning with physical intuitions.

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+Teaching physics standing on your head

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  For physicists, math is the “go to” epistemological resource – the one activated first and the one brought in to support intuitions and results developed in other ways.

  For biology students, the math is decidedly secondary. Reasoning from results (function structure) tends to be the “go to” resource.

  Part of our goal in teaching physics to second year biologists is to improve their understanding of the potential value of mathematical modeling. This means teaching it not assuming it.

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+Goal: Improve student attitudes towards physics.   Previous research with biology

students shows they tend to consider chemistry essential to learning bio, but not physics (or math).

  Traditional physics classes do not do much to change this.

  Tying the physics to biological content definitely seems to help.

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+Results of an attitude survey

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Student perceptions of their attitude shifts (End of Spr. 2013, N=31)

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+Some student comments   “At first I was expecting the class to be like

the biology calculus class that did not focus on any biology. But, as the semester progressed I saw that the class was actually directed towards helping students to understand biological ideas using physics. “

  …[biology professors] have to go over so much stuff that they don't really take the time to go over why things happen. And I'm a very why kind of person I want to understand why does this happen?...And you know [diffusion] was never explained to me very well, and then when I take this [physics] class and understand oh well this is why molecules interact the way they do.

  “I now see that physics really is everywhere, and the principles of physics are used to govern how organisms are built and how they function.”

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+

For papers discussing the development and decisions for NEXUS/Physics and to see current materials

http://NEXUSphysics.umd.edu/

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