Dear Mijo, Please don't put words in my mouth. "Velocity" is a vector quantity, meaning it formally has both magnitude and direction, although we usually omit to specify direction. "Speed" is a scalar quantity, meaning it describes a magnitude only. When the groove is especially tortuous, the angular distance on the arc traveled by the stylus tip with respect to the spindle or the center of the LP is less than the actual distance the stylus travels to get between any two of those points on the arc, because the stylus is wiggling back and forth in order to follow the path of the groove. What I was saying is that each "wiggle" forces a change in velocity, if you were sitting on the stylus tip. (I think it would be like riding "The Whip" in an old time amusement park.) A change in velocity is by definition an "acceleration". Any time a mass (the stylus tip) is accelerated, a Force is required. Since the vector direction of that tiny force is generally in the same direction as the force required to overcome friction, I am suggesting that the two Forces add, which results in one reason why the skating force is never constant. (The other reasons have to do with the ever changing angle by which a line drawn through the stylus/cantilever to the pivot is not tangent to the groove.) Like I said before, this is only my own hypothesis. But it survived my own close examination. I am open to criticism.
