After Rosh Hashanah off, we are back. We started by whiteboarding some unbalanced force problems. Replacing the numbers in some questions with variable does make it much harder. We spent some time just thinking through variables. But systems thinking is helping; most everyone tried to solve the Atwood machine using a block-string-block system, which made me proud.
Then it was off to lab to figure out a model for friction. We thought of three things we could test that would affect friction--the speed of the object, the normal force, and the two surfaces. The speed didn't seem to matter, and since we can't quantify the surfaces, we tested the normal forces. We will debrief this lab tomorrow.
