First, if you have not returned your Quiz 1 revisions, including the original quiz as well as any additional corrections you would like to make, please do so as soon as you can. Some of you did not get Quiz 1 back until Wednesday, so I’m happy to give you a few days extra to complete revisions. But I would like all of them in by Monday, Oct. 16.

Below is a “clean” copy of Quiz 2:

Download (DOCX, 25KB)

You may choose to correct any part of any question on your original quiz (or on a clean copy) and turn that back in with your revision. In addition, you will be expected to turn in a revised solution to what amounts to question 2d from the quiz (whether or not the original answer was correct). The revision is not a correction (though it can also be a correction!) but an opportunity to work on technical communication skills and deepen your understanding of the concepts, as outlined in my post on the revision assignment.

It may be helpful for your revision to approach your work as if 2d were simply the following homework problem:

A sprinter runs a 100 meter race. Starting from rest, their acceleration is 4.5 m/s² for the first 2.5 seconds of the race, after which they run at a constant velocity the rest of the race. What will be the sprinter’s total time for the race?

What you should notice about the quiz is that parts a-c were an effort on my part to guide you to a solution. In part a I invited you to consider what kind of motion this problem represents. It is not constant acceleration throughout (I gave an nonzero acceleration for the first 2.5 seconds; but what is the value of acceleration after 2.5 seconds? Something different!) so you cannot treat the entire sprint using the equations governing constant acceleration. You can, however, break the sprint into two parts, each of which can be analyzed with those equations. Parts b and c asked you to consider just the constant acceleration during the first 2.5 seconds and find the velocity and position at the end of that time period. Beyond offering you extra opportunities to show what you’ve learned and possibly hinting at a method of solution, there was no need for me to ask those sub-parts. Indeed, in MasteringPhysics problem 2.21 about the car approaching the stop sign simply asks for the required value of acceleration, leaving it to us to figure out how to break the motion into segments we know how to model.

Please turn in your revised solution, along with any desired corrections, on Wednesday at 9 AM. Feel free to contact me with any questions about this assignment!

I want to explain in one post the rationale and requested format for the mandatory quiz problem revisions in physics.

I view these revisions not merely as a second chance to obtain the correct answer to a given problem. If that were the chief goal, I wouldn’t ask every student to submit a revision, since many students had the right answer the first time! Instead, I hope you gain two main things from the revisions:

1. A deeper understanding of the logic behind your solution; in particular, the revision opportunity asks you to take time to think about why particular mathematical or physical principles apply in a given problem, and how you know that it does.
2. Practice in clearly communicating physics to others in writing. On a quiz, few of us can take the time to present our work as clearly as we would like. The revisions will come closer to how one might present work in a real-world setting, such as a technical meeting on a science or engineering project or in a research notebook or publication.

To give a brief sense of how I see the difference between quiz work and revision work, this example from a mathematics instructor at Berkeley may be informative:

Download (PDF, 476KB)

You’ll notice that while both are examples of correct answers to some mathematics problem, in the first version it is hard to discern what the problem was, or what the problem-solving logic was. In the second version, the meaning and context of the problem emerge. We know why the writer of the solution took the steps that they did. Some manipulations occur without commentary, but even they are presented in a step-by-step fashion that one can readily follow.

The Physics Quiz Revision Assignment

Your quiz revision should be started on a fresh sheet of paper. I will ask that you use the  IDEA problem-solving strategy (see Problem Solving Strategy 1.1 in the first chapter of Wolfson (p. 10 in the 3^rd Edition). This entails including, in order, and explicitly labeling four steps:

1. Interpretation of the problem – clearly identifying what information is known, what is asked for, and assumptions, laws and principles will likely be employed.
2. Developing a solution. Usually this means drawing one or more diagrams, writing algebraic equations that embody the assumptions, laws and principles that apply (along with brief justifications)
3. Evaluating the solution. Here you will draw on the equations you have identified (and possibly supplemented along the way by well-known math results like trigonometric identities, the quadratic formula, etc.). I will ask that you refrain from plugging in numerical quantities until you have fully solved the algebra for a given variable – in other words, if you’re finding x you should try to get to an equation that looks like “x=(some stuff)” before you start substituting values for variables, if the problem calls for a numerical value. (This is usually – but not always! – mathematically possible in a physics problem.)
4. Assessment of the results – does the solution make sense (magnitudes reasonable, units correct, etc.)? Suppose one considered special cases where a variable gets very large, or very small (perhaps going to zero) – does the symbolic answer you found behave in the way you would expect? Your assessment should be a critical examination of your previous work – actively look for flaws! In particular, you should demonstrate by showing any cancellations explicitly that your units are correct (rather than simply asserting that they are).

More details

Intermediate steps should be logical consequences of previous steps.  If you are going to divide by two and/or move a term from on side of the equation to the other it is sufficient to write the new expression on the line below the previous expression without comment.  Nontrivial steps require an explanation.  If two adjacent expressions are equal, they should be connected by an equal sign (=).  If two adjacent expressions are NOT equal do NOT connect them with an equal sign (=).

If you use an equation from the text, your notes, or another reference, you must document it. Equations should not materialize out of nowhere! In addition to giving the reference for an equation, state why the equation is relevant to the situation at hand.

When you use equations from mathematical tables, show any steps necessary to get the equation in your homework to look like the equation in the table. 

All quantities should have units!  Keep track of your units and show your conversion factors.  Answers without units are usually meaningless (occasionally a dimensionless quantity may be asked for, such as a ratio of quantities with the same units, but this is an exceptional case).

Finish each problem with a concluding statement or paragraph (Assessment).  What is the final result?  How does it relate to the original question asked?  What did you learn from this problem – an application of a theory, a sense of the magnitude of a quantity, a math trick, etc.? Put numerical answers in context (Is this a big number? A small number? Relative to what?). You should also mention useful problem solving details that were illustrated. Use the conclusion to bring yourself to a new level of understanding about physics, its application to real world questions and/or the problem. It is your job to use the language of physics and mathematics in a clear and precise manner to demonstrate your mastery of a problem.  Remember – the most important reader may be you reviewing for an exam!

Scoring: Each problem will be scored on a 10-point scale. Each of the four steps in the problem-solving strategy receives a separate score on the following scales:

• Interpret                    2 points
• Develop                     4 points
• Evaluate                    2 points
• Assess                       2 points

Note that an otherwise perfect answer with no evaluation would receive only 8/10; be sure to comment intelligently on your answers! Notice the heavy weight on the early steps. That’s where the physics lies. So for instance, if you only make algebra mistakes, come up with an incorrect answer but notice that something is awry and tell me how you know there must be an error, you would earn either 8/10 or 9/10.

Example problem:

Download (PDF, 578KB)

Next week will be our first seminar from 9 – 11am on Wed. Oct. 11, which will necessitate some other schedule adjustments already noted on the last page of the Syllabus.

The readings for the seminar focus on issues of representation in the sciences, with emphasis on gender and socioeconomic status:

• “Why Are There Still So Few Women in Science?”
• “Is Science Only for the Rich?”

We will hand out paper copies of these articles in class Monday so that you can mark those with your annotations and questions, and have them available during Seminar (without people using electronic devices during the discussion).

Pre-Seminar Writing Assignment. Beyond reading the two articles, we would like for you to respond in writing to the following prompts. Please type up your responses and bring them with you, along with the two reading handouts, to Seminar. Faculty will check these for completion and they will serve as your Seminar Entrance Ticket.

1. (not for class discussion) Which stories or experiences described in the two pieces are similar to your own? (This response is private; we will not require you to share this writing with anyone else.)
2. (for discussion) What was one specific element of the reading you found particularly striking or surprising? Why? This should be a story, experience, piece of data or research finding. Your typed response should quote, paraphrase, or summarize the element, indicate article and page, and describe why you chose it. (You may choose more than one).
3. (for discussion) What actions or behaviors can students undertake that address issues specifically raised in these articles and fosters an inclusive and anti-bias learning environment in our math and science classroom?
4. (for discussion) What actions or behaviors can faculty undertake that address issues specifically raised in these articles and fosters an inclusive and anti-bias learning environment in our math and science classroom?

• Blank copy of Physics Quiz #1
• Physics Quiz #1 Revisions are due 9am Wed. Oct. 11
  

• Who should submit a Physics Quiz Revision? Everyone should submit a Physics Quiz #1 Revision (details below) at least for the problem indicated (this will be the number in a box on the top of the front side of the quiz for Quiz 1). You may also choose to revise answers to as many of the other problems as you choose.

• Physics Quiz Revision Detailed Guidelines
  • You may utilize any resource available to you, but submitted work must reflect your own personal understanding of the material.
  • The care you take in presenting your work will be considered when evaluating it, so pay attention to organization, neatness, etc.
  • Revisions must be neat, complete, and presented in a logical, clear-to-understand fashion.
  • Since these are revisions, a higher standard will be used to evaluate your responses. Essentially, your revised solutions should be of the highest quality you can produce.
  • You may revise any problems you choose, and must present a complete solution to any problem you choose to revise (not just a part of a problem).
  • For future Physics Quiz Revisions, there will be a designated problem for which you will be expected to apply the textbook’s IDEA framework (as I did in class Wednesday with the Mars lander problem). (This week’s quiz consisted only of unit conversions, which are too simple to make use of that problem solving framework worthwhile.)

You should now find on MasteringPhysics an assignment called Week 2 Reading. This is the Reading Response due at 8 PM Sunday in your weekly workflow. The reading assignment itself is quite long and involves challenging concepts. If you find yourself overwhelmed focus on Chapter 2 and let me know this in your Reading Response.

If you are not yet registered for MasteringPhysics you should still send me a Reading Response. To do this simply email me at caraherj@evergreen.edu addressing one or more of the following questions:

• What section of your assigned reading did you find the most confusing?
• What concepts would you like the instructor to explain in lecture?
• What material was most interesting?

If you have registered for MasteringPhysics you should have completed the Introduction to MasteringPhysics assignment. If you have not done so yet, you should attempt it soon in order to practice using the system well in advance of the Monday 6 PM due date for the Week 1 HW: Ch 1 assignment.

Finally, I’ve added a Physics Primer assignment that has a due date in the distant future. This assignment covers a grab bag of math skills you might wish to practice. It is completely optional; it’s just one more chance to work on any skills you may be struggling with. The topics are

• Scientific Notation
• Calculator Use
• Unit Conversions
• Working with Fractions
• Simplifying Algebraic Expressions
• Solving Two Equations and Two Unknowns
• Interpreting Graphs-Lines
• Right Triangles
• Inverse Trigonometric Functions