- 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 journal will be created 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)
- Read "Lab Syllabus", "Creating a Lab Journal Using Excel", "The Motion of Free Fall" and sample lab journal
- Students should also bring their personal laptop next week
- 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
- Students will download the data file Excel Graphing Exercise.xlsx directly to their personal computer or a lab computer (an extra copy is found
on the T: drive, in the Phys103 directory)
- Note about 2-Factor Authentication (2FA) on lab computers: If students use a lab computer for the Excel exercise, they will login 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
- Students will work on the Excel exercise in groups; print one copy of the completed graph for the group with all members' names
- 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 data they will edit and use; page 2 has the graph (August 2025 - I have renamed L to D, but the data and graph remain the same)
- Position & Time:
- 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)
- Here are the solutions to this exercise (08/19/2025 - Increased total points to 35; still need to redo individual point deductions!)
- Students download five Logger Pro files from Canvas to the lab computer.
- 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.
- 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:
- Students download five Logger Pro files for the separate motions. If they open them by double-clicking, the motion sensor won't be recognized. Close the previous file before opening another so the motion detector can be seen by Logger Pro
- If students drift left or right, or hold 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, but then they have to walk on our gross floors in their stocking feet or barefoot. Eww.
- 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. Not that they ever read anything before lab.
- 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. I use "Position and Time 2", which is the first graph they have to match. All files are on the T: drive, in the Phys103 folder, so open it from there for the demo. I ask the group to explain to me the motion and approximate distance ("close" or "far away") for each of the three segments of motion they will match. Then I demonstrate the motion. 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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