Enhancing Student-Student Discussion in Recitation & Laboratory: A Conversation

Stephen Van HookDept. of Physics

Contributing faculty:Kirsten Purdy Drew

Dan CostantinoEric Hudson

And lots of TAs who have provided input:George Paily

Aruna KesavanMichael KoopAsher Evans

Ross Martin-WellsSteven Consevage

... and more ...

Thanks to Jackie Bortiatynski & the Center for Excellence in Science Education (CESE), Eberly College of

Science, Penn State University

One afternoon several years ago the writer was asked to proctor an examination in elementary physics to be administered to a large room full of army trainees. As he strolled the room waiting for the examination to begin he overheard many snatches of excited, apprehensive conversation – of which one significant piece has haunted him ever since: "Sure, I know F = ma, but what’s F? what’s m? what’s a?"

- Robert Weinstock, Am. J. Phys. 29, 698 (1961)

Quoted in http://www.physics.indiana.edu/~sdi/sdi-6.pdf

Physics is not calculating - it’s knowing what to calculate & what the result means!

If I had asked, “At t = 2.04 s, what is its vertical position and vertical component of velocity?” it

will have been trivial.

Explicitly address known common misconceptions

Work-Bow & Arrow recitation: As F decreases, W still increases

(W is related to the area of the F vs x graph

Newton II lab: As F decreases, v still increases (once again v related to the area of the F vs t graph)

The overuse of proportionality, especially with Force

For example:

Peer Review is an important skill!Team work in class & piazza

discussions attempt to develop this skill.

Inspirations:

POGIL - making sense of data

McDermott et al Tutorials (U Washington) - conceptual-focus

Modeling Method - David Hestenes (ASU)- models, not just equations

Recitations

50 minute periodsonce a week

Groups of 324 students & 1 TA

Not a change in the activities, but in the arrangement of the

room!

Storyline (especially for recitations)

Inspired in part by John Meier’s talk to the STEM group on graphic novels in STEM teaching & other articles I read about that same

time about how humans are driven by story & narrative.

Sam Spade (Newt Einstein) - Cirque Nittany Case

“As private consulting physicist Copernicus Brown, you know that you need to keep your physics skills sharp – you never know if you’ll get a client with a problem that requires projectile motion, forces, energy, momentum, or even oscillations. This morning, as you sit in your dorm room that also serves as your office, simple harmonic motion seems to be the problem du jour.”- The Pendulum Paradox

“As R. Blake, the intrepid captain of the space ship Liberator, you are approaching a solar system on the outer edge of known space (known to your species, at least). You are looking for planets for possible colonization and you are most interested in one of the planets (you’ve named it Planet X), which happens to have a moon orbiting it.” - Planet X

“Most mugs make the mistake of trying to work in numbers and are always getting out their calculator to clatter its stupid keys. Besides being a waste of time, at the end all they’ve got is a number and they haven’t understood anything about the problem itself. This is where you have a huge advantage if you can work in variables. Once you learn to use variables you’ll solve problems quicker and also be able to see patterns in the solutions that would not be visible to those saps just working with numbers.” – Newt Einstein, Confessions of a Private Consulting Physicist.

On this hot muggy day, you are sitting in your office, leaning back in your chair, sipping iced tea and watching the ceiling fan slowly spin when the door opens. A large man strides in, clearly in some distress. He is oddly dressed in an old-fashioned tuxedo, top hat, and sporting a long, curly mustache. “Are you Newt Einstein, the famous private consultant physicist?” he asks pointedly. You casually point to the sign on the door: Newt Einstein – Physics is everywhere and we’ll investigate it for you. “I have an idea for a new act for my circus, Cirque Nittany,” he announces its name as though he’s addressing the entire room not just yourself, and you note to yourself that this explains his odd attire. “However, I need your help making it safe for my performers. We’ve had a broken arm and some broken ribs already. Valentina and Igor refuse to attempt this number again until I solve this problem and we have a show tonight at the Bryce Jordan Center!”

You gesture towards the chair in front of the desk and he sits down and describes the following circus act: an acrobat (A) runs off the end of a horizontal, elevated platform. The edge of the platform is directly above the muzzle of a cannon. At that instant, a human cannonball (C) is shot out of the muzzle (opening) of a cannon. When the acrobat and human cannonball meet mid-air, they are supposed to grab each other and then fall together onto a net below them. “The problem,” he says, “is that sometimes they miss one another; and other times they hit one another so hard bones are broken. We can’t afford trial and error anymore – so I came to you.”

“You’ve come to the right place,” you assure him, energized now that you have a case. “Physics is everywhere, and we’ll investigate it for you!”

(fake quotation - foreshadows lesson on variables)

Art in the Balance (Center of Mass & Equilibrium)

Conceptual focused - not calculation-focused

It’s all about the discussion!First version of the Cirque Nittany Case:

Essentially: “Write the equations of motion for this situation”

Better version of the Cirque Nittany Case:

“I went online and found these,” he says, and shows you the set of equations (below). You look what he’s written and say, “We’ll they’re a start, but we’ve got to correct a few things. I see something wrong with each equation – and you are missing one!” What’s wrong with these equations and how should they be corrected? What equation should you add that’s missing?

(a) xA(t) = vAt – ½gt2

(b) zA(t) = ½gt2

(c) vAx(t) = vA – gt

little discussion & usually wrong

much more discussion & usually right

ScaffoldingIn Miner’s Coffin, original version (predated me) was all 3D

vectors & numerical - students struggled with understanding it

New version scaffolds by doing it in 2D & graphically

Experimental ProcedureAt the end of the day, when all the customers have left, Jocelyn calls everyone together. “Our competitor down the street, Pizza Hike, claims that their pepperoni pizzas have more pepperoni than do ours. I’ve asked Pat and Chris here to independently test that claim, so let’s hear what they have to report and do some peer review of their studies.”

Pat says: “I bought one of their pepperoni pizzas and counted the number of pepperonis on it compared to one of our pepperoni pizzas. I counted 22 on ours and 18 on theirs, so their claim is definitely false.”

Chris says: “I bought four of their pepperoni pizzas and cut a 15 cm x 15 cm section out of the middle of each one, removed all the pepperonis from that section, and then weighed them. I then did the same for four of our pizzas.

7. In what ways does Chris’ approach (and description of the approach) improve upon Pat’s approach (and description of approach)?

In lab we often have to decide: are these two numbers really different?

Always a secondary messageImportance of using variables

Cirque Nittany case: An acrobat & human cannonball meet in mid-air

What sets the relative speed at impact?

What if we did this act on the new moon colony?

many parameters cancel out

(something you wouldn’t see if did it with numbers)

After looking at flat curve with friction (q3), and banked curve without friction (q8), determine which possible expression for a

banked curve with friction is possible.

More discussion than in doing algebra to solve for it

Limiting Cases

LaboratoriesOnce a week

115 minute periodsGroups of 3

48 students & 2 TAs

Computer-based data collection & graphing systemMicrosoft Excel

Open-ended Labs

Need to know how to use the equipment well enough that they can determine

what to do, not just follow explicit steps.

Less directions on what to do; more on what to think about before doing the

experiment

CRASH LAB! You have been charged with answering these specific questions from actual crash data that you will collect:

I. Is an individual vehicle’s linear momentum (p = mv) conserved during a collision?

II. Is the total linear momentum (P = p1 + p2) of the system of two vehicles conserved during a collision?

III. Is the total mechanical energy (E = K + U) of the system of two

vehicles conserved during a collision? (Is it the same before & after the collision?) What about just K?

IV. Does the type of collision – that is, whether the vehicles bounce off

one another or whether the vehicles stick together – affect what happens to the momentum and the mechanical energy?

V. In a collision between a stationary vehicle and a moving vehicle,

which vehicle experiences the larger change in momentum?

VI. In a collision between a more massive vehicle and a less massive vehicle, which vehicle experiences the larger change in momentum?

For each question, provide a reasoned argument based on your data and show appropriate graphs and/or tables to support your arguments. Remember that a single experiment or data point is often not enough to be convincing. You need clearly explain how you accounted for friction. Just showing a graph is not sufficient since you must explain what the graph shows; in addition, think carefully about how you present your graph.

No procedure given.

They need to determine what measurements and graphs to make & what they mean

Fitting Functions (esp. linear) to data

Why do we do this?What are y and x in the linear fit?

What do the #’s (5, 4.01, 0.99972) in the fit mean?

!

Having them explicitly connect the fit expression to their physics equation for the situation

Effective Graph Presentation

Use the full real estate!

What point are you trying to make - constancy or variation?

Crop data to relevant sections - otherwise we don’t know that you

know what’s important!

Q4. A graph of a different experiment is shown below (the actual experiment ran from 0.5-3.5 sec). How could the presentation of this graph be improved? (This is an important question since effective presentation of graphs is a valuable skill to learn – and your grade on this lab will depend on how well you present your graphs.)

!

Scaffold to limit the cognitive load

Point out when a new tool is being used and have them spend time learning how to use it (explicit

instruction) + some exploration

Whenever I failed to follow this principle,

there were problems!

We don’t “verify” laws but look at how well particular models apply

Looking explicitly at role friction will play in motion

• While these are low-friction carts, they are not zero-friction carts, so how will you account for friction in interpreting your graphs? (For example, if the kinetic energy is decreasing over time, how will you separate any change in kinetic energy due to the collision with the change in kinetic energy that would have occurred during that time just due to friction?)

On the left, draw the momentum-time px(t) graph for a block moving to the right that hits a wall and then bounces back with half the speed it originally had (assume no friction). On the right, draw the diagram if friction were present.

! px!

t!

! px!

t!

Implementation Issues

TAs not doing it the way it’s supposed to be done (often

wanting to short-circuit discussion instead of letting

students struggle a bit)

Students not doing it the way they are “supposed” to do it - usually because they didn’t read it

(sometimes because they couldn’t read my mind)

Time (never enough of it!)

Shifting focus from “an activity to get (race) through so we can leave” to “a 50 (or 115) minute period to spend developing a better understanding of physics”

Frustrations (esp lab):

Using prior ideas instead of their own data to respond to questions in lab

Not connecting idea A to very similar idea B that they just answered a question on.

They don’t always make connections that we think should be obvious...

and they don’t realize when their ideas are internally inconsistent!

To date, have written or significantly modified:

PHYS 211 (mechanics):18 Recitations9 Laboratories

PHYS 212 (electromagnetism):3 Recitations

3 Laboratories

These activities are not perfect!(perfect is a meaningless word in this context)

These activities should be continually improved

Times change, our students change, our understanding of teaching & learning changes.

Or we get bored with the same activities!

My philosophy (I’m sure said more eloquently by many others before me):

If you’re not improving you are falling behind!

Noah Finkelstein: “Educational problems don’t stay solved!” .However ... a word of caution ...

The Little Big Things: 163 Ways to Pursue EXCELLENCE,Thomas J. Peters(co-author of In Search of Excellence)

Don’t sand down all the rough edges - some edges need to be

rough!