1. The problem statement, all variables and given/known data This is not a homework question, just a problem I want help solving. Don't be afraid of giving too much of the answer, I am not even in a physics course right now. When setting up a turntable/record player, you need to dial in an "antiskate force". This is an outward applied force on the arm to make sure the needle sits in the middle of the record groove. It counteracts centripetal force. What we are trying to figure out, is how much anti skating force is required to counteract the centripetal force on the record needle. Perhaps derive an equation for the force required with a given position on the record. The arm is on a pivot 21cm away from the center of the platter, and the distance from the pivot to the needle on the arm 23cm. The needle is moving towards the center of the record and therefore the radius of the rotation is changing. This means that the velocity of the stylus relative to the record is changing, even though the platter spins at a constant 33rpm. The record grooves have modulations, they wave back and forth under magnification, they have bumps on their walls. A constant downward force of about 2grams is applied by the tonearm. 2. Relevant equations Fc=m(v^2)/r Is friction somehow involved? 3. The attempt at a solution No idea where to start. I guess some sort of force diagram.