1. Experiment 4 part 1 – Feedback and recap of Experiment 3 – Lab 4: Coefficients of Friction Goals for this lab: o How can you measure the static,  S, and kinetic,  K, coefficients of friction for a block? o How can you determine the uncertainty (ie, error) of the coefficients of friction? N FgFg F f=  N

2. – Get to know the equipment to measure forces: How does it work? How sensitive is it? What block are you going to use? Experiment 4 part 1 – Design an experiment to measure the static and kinetic coefficients of friction: How are you going to measure the coefficients? How are you going to find the uncertainty in your measurements? – Collect and analyze data – Group discussions Sample data from previous groups.

3. Things to think about – Does mass matter? – Which measurements are more accurate: the ones with lower mass or higher mass? – What made some measurements better than others? What was different in the way they were measured? – What is a good way to calculate the uncertainty? Can you use it for other experiments (for example, terminal velocity)? – How can you reduce the uncertainty of your measurements?

4. Courtesy of xkcd “As the coefficient of kinetic friction goes to 0, productivity goes negative as you pull OTHER people into chair-spinning contests” (http://www.xkcd.com/815/)