Lecture 6

Judge of a man by his questions rather than by his answers. Voltaire

Paper on Doppler velocimeter. Note the similarity to the Doppler lab expt. http://iopscience.iop.org/article/10.1088/0022-3735/14/8/029/meta

First explain what’s going on. Understand the principle Use Moire pattern to illustrate interference https://en.wikipedia.org/wiki/Moir%C3%A9_pattern Critical Thinking skill “how to spot an assumption” is related to assuming turbulence effects the determination of particle speed using this technique. http://web.mit.edu/fluids-modules/www/exper_techniques/LDA.text.pdf http://www.dantecdynamics.com/measurement-principles-of-lda http://users.ece.gatech.edu/~gtz/java/autocorr/index.html

The intensity oscillations tell time per fringe traversed. The fringe spacing is given by the laser wavelength and angle the beams are crossed. The particle speed is this fringe distance divided by this traversal time.

Critical Thinking skill: how to spot an assumption. To get the particle speed what assumption is made? All the particles travel with the same velocity vector. What if there is turbulence causing particles to move at a different angle thru the interference pattern? Like moving the reflector in the Doppler lab at an angle so it doesn’t move in the direction of the microwave beam? There is extra distance travelled for the time to go thru a fringe.

This paper illustrates citing the results from the model rather than deriving them. This corresponds to the Critical Thinking skill “how to tell if a source is reliable.” Also note the citations to Robert Brown who visited this week.

Then note that in the error discussion no statistics are described. The author is not trying to show that the data support a model but using the data and model to determine how turbulence affects this technique of measuring the particle speed. Note how the parameters of an equation are defined and the eqn not derived but cited. Note how this doesn’t follow the format of a lab report we use. Why?

Practice asking questions

Watch the pendulum link here https://www.youtube.com/watch?v=yVkdfJ9PkRQ

Then hand out paper on which you must write 3 questions each of which must be in a different category. Those of you who think this is trivial ought to try and come up with questions in the analogy and creative categories.

-emphasize the informational questions: how do you know that? Why did you do that (repeated)? What are the assumptions and conditions for which the model is valid? -emphasize the analogy question, “is this related to the orbits of the planets?” A peg on a rotating circle executes simple harmonic motion when viewed “end on.” If each peg were a planet rotating at a different rate, then the end-on view would look like masses attached to springs with different spring constants. Would these masses line up after some time?

Critical thinking at CSM

-go thru the CSM bulletin (the legal document between you and CSM) to find the value prop. Note how no promise is made that you will graduate with this value added. There is no statement that you “will learn” these characteristics when you graduate. Rather it is “must have” and “should have.” http://bulletin.mines.edu/undergraduate/welcome/ Here are more comments on critical thinking http://bulletin.mines.edu/undergraduate/programs/appliedscieng/

Homework for next week

Next week I will ask questions about chapters 8-10 of the "How to lie with statistics" while you will ask questions on another video. A copy of this book can be found on the wiki. Just click on the book to turn pages.