Q: Why does the motor usually use ball bearings and not others?

The bearing used by the motor is a part that supports the shaft. It can guide the rotation of the shaft and can also withstand idle parts on the shaft. The concept of a bearing is very broad. There are four types of motor bearings commonly used in motors, namely rolling bearings, plain bearings, articulated bearings, and oil-containing bearings. The most common motor bearing is a rolling bearing, that is, a bearing with rolling elements. Sliding bearings generally refer to bearings without rolling elements, that is, bearings for sliding motion.