1. The problem statement, all variables and given/known data I have solved the problem where one mass m1 is on a horizontal frictional table connected to a mass m2 which is hanging off the table by a string over a pulley (assuming pulley massless), assuming that m2 is greater than m1 there is a net acceleration causing the mass 2 to fall down and the mass 1 to follow. The problem is that the equations suggest that an increased pulling force (i.e. larger m2) causes an increased coefficient of kinetic friction, furthermore I apply this formula to the data I have and indeed a larger hanging mass gives a greater kinetic friction coefficient. Is this correct? I would have thought it should not effect the coefficient. 2. Relevant equations 3. The attempt at a solution Solution already obtained, the question is about the solution.