TA/LA Training Reminders from 2/12, for the week of 2/15 (Lab 2, Part 1)

Here are the reminders that I promised you regarding the Fri. 2/12 Lab/Recitation training.  I have also included links to readings that you may find helpful--to understand what the students know about resistive forces and the language the professors will use to discuss resistance, as well as a link to the system schema page.  Good luck this week! ~KIM

1) Recitation: Forces for Objects and Systems

Link to recitation: http://www.physics.umd.edu/courses/Phys131/spring2014/Labs/Forces%20tutorial.pdf 

For more info on system schema: http://umdberg.pbworks.com/w/page/68452162/System%20Schema%20Introduction%20%282013%29

(Break--Pass back Lab 1, Part 2, if graded.)

2) Lab 2, Part 1: Directed Motion & Resistive Forces

Link: http://umdberg.pbworks.com/w/page/68933700/NEXUS%20Physics%20Labs%2C%202013-2014

** New lab groups for this two-week lab.  Also, new jobs/roles--if you are using them.  (Record the new roles--keep track so that everyone eventually does every job this semester.)

*** When you have the Lab 1, Part 2 grades ready for your students, please hand back the reports.  All students should have their labs graded and back in their hands before they turn in their next lab.  (So hand them back at the start of lab during the week of Feb. 22nd, at the latest.)  I always tell the students that "The Checker keeps the lab," that way each student has one example of a graded lab in their possession by the end of the semester.  Do it however you like (perhaps the Journalist keeps it), but be consistent within your own sections. 

**** Here are the readings the students have done/will do that relate to resistive forces.  Scan through them to get a feel for what the students do/will know and what language you should be using (in order to be consistent with the professors):

http://umdberg.pbworks.com/w/page/68392695/Resistive%20forces%20(2013) (Page on Resistive Forces--contains links to readings on Friction, Viscosity and Drag--review these, too!)

a) Before you have the students start the experiment, you should discuss the concept of terminal velocity with them.  Ask them to define it.  Have them draw what this would look like on position vs. time, velocity vs. time , and acceleration vs. time graphs.  They have not studied terminal velocity yet, but they certainly have the background to understand the idea.  Also, they may not have learned much about resistive forces yet, but by the time they need to analyze their data (next week) they will have had sufficient exposure to the concept and plenty of practice solving problems with resistive forces.

b) Please make sure students aren't planning to analyze too many videos.  Each video analysis takes about 5 minutes. Even analyzing the videos on two computers (analyzing 'in parallel'), the minimum of 10 to 12 videos (4 to 6 for investigation 1 and 6 for investigation 2) that students will have will still take them quite a long time to analyze.  They need to have modeled the situation, designed their experiments, collected the videos, and harvested ALL the videos using ImageJ within this first week.  Since we only have 110 minutes of lab time, students should not go overboard in video capture!  Remember, since these VIDEO data sources are so rich, the need for multiple 'trials' is reduced--our velocity statement off of a single video is MUCH more accurate than a stopwatch-and-meter-stick measurement could produce.  If students insist on multiple trials, allow them TWO at most.  Also, the capture rate of the webcam should be around 30 fps (at a medium resolution, saving to the computer's hard drive).  I students try to record using VirtualDub directly to a flash drive or at too high a resolution, this will hurt the capture rate (dropping it as low as 7 fps)--please warn them!

c) Remind the students to keep a careful record of the UNCERTAINTIES in each video/measurement.  They will need this data for the error propagation and model-fitting that comprises the second week of this lab. Students should also be careful to NOTE the AVERAGE FRAME RATE used by Virtual Dub. The uncertainty, average rate, and pixel-to-distance conversion will be UNIQUE to EACH VIDEO!!

d) Please make sure that students are CAREFUL when transporting the large cylinders of glycerol solutions. If any of these spill, we are SOL (as we have no spare glycerin to make new ones)!  Also, the edges of the sphere/ball 'scoops' may be sharp--have them handle these with caution. It may help to have students move their backpacks/bags/jackets/etc. against the walls or under their lab tables (to prevent tripping). As there are only two of each concentration, students will need to share the glycerol cylinders. They should put the cylinder back on the equipment table as soon as they have finished taking the video(s) of that cylinder. In the event of a sphere/ball 'escaping' the scoop, Don's clever 'retrieval scoop' is in the extra (and fluidless) cylinder on the equipment table at the back of the room. If necessary, there is a funnel and a bucket in the under-sink cabinet. Also, the glycerol will likely ruin the whiteboard markers, so it is important that they wipe up spills as they go and try to contain any drips/splashes.  The red plastic caps should be placed back onto the cylinders at the end of each lab section.

e) The equipment students will need is on the back, left table of the room or by the sink in the front.  Make sure the equipment returns to these locations at the end of your lab (so that it is out of the way during the next section's recitation). If you teach the last lab of the day, please be sure to cap the graduated cylinders.  If students need to reference the Excel or ImageJ tech documents, these are in the paper/file holder by the printer.

f) Please have students clean up after themselves before leaving the lab room--wiping up any spills and throwing out the paper towels, putting equipment back where it belongs, and sorting and stacking the recitation and lab documents at the front of the room.  They should also erase their whiteboards. If the whiteboards become hard to use, due to the glycerol, then there are whiteboard wipes available for cleaning them.

g) EVERY student should save a copy of his/her lab group's data and word files before leaving the lab.  These files should be copied onto a flashdrive, sent via email, or placed in a 'dropbox.'  If any videos are still un-harvested (not yet processed with ImageJ), then these videos also need to be saved.  Any information left on the lab room computers WILL BE DELETED and unavailable for week 2. EACH student needs to have a copy of ALL of the data the group has created (spreadsheets and word files).  Remind them at the start and end of the lab period.

Please let me know if you have any questions or comments!