Question

why do we use ball bearings in shaft of motors​

Answer 1

Answer:

The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. ... Ball bearings tend to have lower load capacity for their size than other kinds of rolling-element bearings due to the smaller contact area between the balls and races.

Answer 2

Answer:

Ball bearings provide very low friction during rolling but have limited load-carrying capacity. This is because of the small area of contact between the balls and the races. They can support axial loads in two directions besides radial loads. Ball bearings are used for controlling oscillatory and rotational motion.