What's Your Size?

Physical Science - make sure that you complete your measurement lab activity tonight so that we can discuss the results/methods tomorrow. Note: significant figures is a main focus of this lab, so be very aware of significant figures when your make your volume and density calculations. Watching folks today, it was good to see groups discussing procedures and methods rather than barreling along with no firm plan. A few tips:

1. Keep an eye on the time and make sure measurements are collected while in class. Questions, analyses, calculations, etc. can be completed at home, but data collection is an in-class only activity.



2. Choose measurement tools with an eye towards precision. I noticed that a few people chose measurement tools that were not optimum for the object that they were measuring. This lab purposefully does not specify exact tools and I provided a variety from which you could choose. A micrometer would be inappropriate to measure the large cardboard box, but would be the best choice for a small sphere or for the thickness of an index card. A number of people massed their objects using the large digital balance. That balance has a sensitivity of increments of 1 gram - it doesn't report any fractional values in-between. I saw a few measurements for mass of 1 gram. The smaller balalnce had a sensitivity of 0.1 gram. This would have given you an additional significant figure (more precision) for your mass measurement. A 1 SF mass value means that your density calculation for that object could also only have 1 SF.



3. Put everyone in the group to work. Don't allow slugs or equipment hogs. Rotate jobs, divide tasks - make sure everyone contributes and no one tries to do it all by themselves.

Physics - Quick note: if you want a hard copy of the textbook, we now have enough to go around. Bring back the disc that I gave you at the start of the year and I'll check out a book to you. If you want, you can just keep the disc, but you can only have one or the other. Remember, the book is also online. For lab today,as groups found, mentally-moving from position/time to velocity/time graphs was a challenge. However, the labwork emphasized that even though graphs may look alike, their meaning may be nothing alike. Always study the variables on each axis and reflect on what the graph shape indicates about these variables. Many people approached their velocity-time graphs by stopping when they saw a flat, horizontal line on the computer screen. Unless that line was at y=0, it meant keep walking with constant velocity! We will go over these in class tomorrow and add another descriptor of motion to our toolbag - acceleration.



Honors Physics - Tomorrow's lab will provide a very precise measurement of acceleration due to gravity at our location. Our test object is minimally affected by air resistance, but one of the extensions to the lab protocol will add air resistance so that you can see its impact on free-fall motion. As for the homework problems from last night, people seemed to do fairly well, but if you think that you require more practice, see me for additional problems. It is important to be very comfortable using these formulas and thinking through motion problems as we rely on these skills often this year.