We did a lab in physics class to determine the coefficient of static and sliding friction. basically we used a spring scale to determine how many newtons of force was required to just get a block moving and then to keep it moving. We needed to do several trial runs with a slow, fast, and faster pull. After the block was moving, the coefficient of sliding friction were all about the same, however the coefficient of static friction became larger when we pulled faster. My teacher was unable to give me an explanation and told me that velocity should have nothing to do with coefficient of friction because it is not in the formula(Ff=uN). It makes sense to me that if you are trying to accelerate the object faster, it is going to take a lot more force to get it to move than if you are increasing the force little by little until it just barely moves. Can anyone help me understand?