Physics: What does a balance measure?

A couple of students turned in their work from yesterday to my sub, and I saw they pretty consistently interpreted the balance in the video as measuring mass rather than force. To help clear that up, I took a balance on the school elevator and recorded some video. We started by drawing some free-body diagrams, then connected those to changes in the reading on the balance to get at what the balance is really measuring. From there, students whiteboarded and shared their answers to yesterday’s activity.

Chemistry: Isotopic Pennies

To introduce the idea of isotopes, students got sealed jars with 10 pennies and had to determine how many of their pennies were made before 1982 without opening the jar.