Hello, Here is my question: should the kinetic friction coefficient Fk be the same when the object with mass m is pulled with a constant velocity as the kinetic friction coefficient with the same mass m when it was pushed and released. The measurements in the second case were taken from the decelerating part of the Force vs. Time graph. I have several table with data many of which i have calculated myself. from the formula: Fk = ;mu * Fn Fk - kinetik friction force, ;mu - coefficient of friction kinetic force Fn - normal force in the first case I have: m = 0.09 kg Fk = 0.1387 N (the uncertainty here is 17% !!! Fk = 0.1387 +- 0.0238) Fn = 0.882 N => ;mu = 0.1573 In the second case: m = 0.09 kg Fk = 0.2585 N Fn = 0.882 N => ;mu = 0.2931 here i also have uncertainty in acceleration which I use in order to find Fk. So, my question is: Should the coefficient ;mu be different in two cases or do I have such a big error? THANKS!!