I teach an AP/IB physics class in a high school. On the last IB ("International Baccalaureate") examination, there was a question about friction that went like this: [an object was described to be at rest on an incline] "Show that the object must start to slip when the angle of incline is 45 degrees or less." The IB is convinced that a coefficient of friction cannot be greater than 1.0 . I and many other physics teachers across the globe scratched our collective heads at this. What are we supposed to do with all the tables and textbooks that describe coefficients of static friction which are greater than 1.0? Rubber on pavement, for example (1.2--1.4) . The report issued by the IB organization says "teachers are advised to tell students that when the coefficient of friction appears to be greater that 1.0, factors other than friction must be considered." I am at this moment looking at a rubber stopper at rest on a sheet of 150 grit sandpaper (stapled to a board) at an angle of nearly 50 degrees. I need to know, what is not "friction" about that?