- Computers are needed for lab this week
- Room swap this week with Phys151; the "Position & Time" experiment requires more space to spread out, so the larger lab is used
- A "real" lab report will be written next week, so hold off on the discussion of format until then
- On the blackboard, I've written the tasks for next week. Please emphasize these to students:
- Meet in regular room (BH 204 - next to Einstein mural)
- Print & read "Lab Syllabus", "Intro. to Lab. Practices", "The Motion of Free Fall" and sample lab reports
- This week – two independent exercises are performed:
- Graphing & Curve Analysis
- Students use a given data set to create a graph, apply a linear curve fit with appropriate fit equation, properly labeled title and axes
- The data file Excel Graphing Exercise.xls is found
on the T: drive, in the Phys103 directory
- Note about 2-Factor Authentication (2FA): Students login to each computer using their SLU accounts, but as of Fall 2023 they also need to login to Microsoft and pass the 2FA challenge (on their smart phone) when they start Excel. If they don't login to Microsoft, they'll get an error message when they open the spreadsheet and won't be able to insert a graph
- Have students do this after the Position-Time experiment
- I've added an "Analyzing the Graph" section in the directions. This details the procedure of rearranging a model equation in the form of the fit-function used on the graph. I intend to emphasize this as the procedure used every time we have graphed data, to (hopefully) minimize the number of people who want to calculate slope for each data point. They are asked to write the velocity (= slope) on the graph. If they don't get this, you're in for a long semester
- Problem: Despite a clear notation on the lab list page, they don't print the Excel instructions in color, and miss the fact that I've color-coded the relationship between the model equation and the best-fit equation!
- Do this in groups; print one copy of the completed graph for the group with all members' names
- Students working on laptops can unplug the computer and take it back into the lab to complete the Excel exercise
- I don't usually grade this; I just check that they've created a graph with the correct fit and all associated elements included. Be sure to chastise students who did not follow the instructions
- They want to remove the grid lines, based upon their experience in Chem lab. I've added an extra line in the instructions telling them to leave the grid lines in place
- Here's my copy of the graph showing what students should produce from this exercise. Page one has the graph they will create; page 2 has comments pointing out which elements they should have included
- Position & Time:
- Here are the solutions to this exercise
- Use a motion sensor to study the difference between velocity and acceleration
- Up to eight setups will be available, depending on the maximum number of students in each section. Students should be encouraged to work in groups of two (unless you have an odd number of students in total). Jeff will put out laptops and move carts before each lab in the following positions:
- Three setups in Bewkes 231: two desktops & one laptop (near sink)
- Three setups in hallway (laptops on carts)
- Two setups in Bewkes 202 (Modern Physics Lab - if needed)
- All motion detectors should have been set to 'human' by moving the switch to the right!
- Students answer the questions that appear throughout exercise, and write their answers directly on the instruction pages. They should write in complete sentences!
- Students work in groups, but each person will hand in a copy of their answers
- Predictions are not graded, but they'll lose points if their measurements don't match prediction and they say it does
- The best signal is obtained by students holding the wood drafting board in front of them as they walk backwards (so they can watch their position traced on the computer screen)
- Is it better to hold the board horizontally or vertically? Who knows? I hold the board horizontal, and I don't get spikes in the signal when it loses me. Some students hold the board vertically. Whatever works, I suppose
- Each station has a meter stick and 30-m tape measure so that students can estimate their starting position
- Matching scores don't matter, but here's my approximate scale:
- 0.3 – ok
- 0.2 – good
- 0.1 – very good
- <0.1 – Excellent!
- Problems encountered:
- If students drift left or right, or holds the board too high or two low, the motion detector can lose track of them and pick up their body or a nearby wall. The board should be held with its midpoint at the height of the motion detector
- The board shouldn't be jiggled, and should be held perpendicular to the floor at the height of the motion detector
- Yes - you can cheat! Move the board in/out to better match the desired motion. Shows an understanding of what's actually happening
- Students sartorial choices can interfere with their ability to walk backwards. If it's hot, they'll show up in flip-flops. Some have come in ridiculously high heels. Kicking off their shoes solves that problem
- And, yes, students will come to lab without their contacts or eyeglasses, which doesn't help if they're near-sighted. Since I frequently forget to send a reminder through the course instructor, I've added a note about appropriate eye- and footwear to the page where they download their lab instructions
- Be sure to point out to students the difference between the way the graph indicates you should move (with sharp transitions between "at rest" and motion) and how they actually move
- I always do a demo for the students. All files are on the T: drive, in the Phys103 folder. I use "Position and Time 2", which is the first graph they have to match. This requires a lot of practice on your part to do it well, and gives students an idea of how well they can match their motion. I tell them that they can challenge me if they think they're really good at it, and several enjoy that challenge. Many won't care enough to try to repeat a measurement to improve their score.
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