I have always found that students have a hard time distinguishing between static and sliding (kinetic) friction. After this lab, students don’t have that trouble any longer! This lab does require some patience as some of the numbers can be difficult to measure, so encourage students to take their time and get good results. It is helpful if you can do this lab ahead of time and know which spring scale would be best for students to use. Be sure to select the spring scale that will provide them with the most accurate results. If students will need to use more than one spring scale, then provide students with that information prior to the lab and save some frustration for both them and yourself during the analysis!