I remember doing an experiment in Physics class to find the coefficient of friction with gravity. We set an object with a flat surface on top of a ramp, and adjusted the ramp angle so that the object would move down the ramp at a constant velocity. Then we measured the angle of that ramp to find the force of gravity, then solved for friction. I was just wondering... we solved for the coefficient of kinetic friction, right? But doesn't the experiment show that kinetic friction was actually greater than static friction? The force of static friction was unable to be great enough to prevent acceleration, yet the kinetic friction is great enough to prevent acceleration. Or were they both the same? No... that wouldn't work, would it? In that case, because kinetic friction = applied force by gravity, static friction would be just enough to prevent acceleration... but the block did move. It seems that in every case where an object moves down a ramp with constant velocity, kinetic friction is higher than the static friction threshold. I don't think it would matter what material we used, just as long as we don't use, let's say, something with velcro-strength friction. I don't understand: why is this so? Is there something we didn't account for in this experiment?