Question

how does oiling and using ball bearings help reduce friction

Answer 1

→Friction is caused due to the irregularities between the two surfaces in            contact. Though an object might appear smooth when we touch it, at the microscopic level there are irregularities.
→When we oil the surface of the object, we are filling the minute irregularities to a certain extent. Thus, a layer is created on which the other substance can move easily. 
→Rolling friction is of a lesser than sliding/static friction. When ball bearings are used, the linear motion between the bodies is converted into rotational motion between the ball bearings and the second body. Thus, rolling friction comes into picture and thereby making it easier for us move objects.

Answer 2

Heya user!!

When ball bearings come in contact with oil due to the rotational force between 2 bodies...friction is reduced!!

Hope it helps