how to change linear motion to rotary motion
Reciprocating motion A crank can be used to convert circular motion into reciprocating motion, or conversely turn reciprocating motion into circular motion.
Turntable anti-skating Due to the offset between the cartridge's axis (which is approximately tangential to the disc) and the tonearm's pivot, the force applied (through friction) by the rotating disc to the cartridge tends to draw the tonearm toward the center of the record and distort the balance of the sound and of the wear suffered by the stylus and the vinyl groove. To prevent this, an appropriately-sized opposing force (a rotational torque) is applied at the tonearm. This is accomplished in various ways by dedicated mechanisms, depending on the tonearm's manufacturer, and ranging from a small counterweight adjustable by a knob, to adjustable spring or magnetic mechanisms, usually calibrated in grams of force.[1]