Question

Ball bearings reduce friction because they___ rather than slide.
A) Roll
B) Swing
C) Bounce
D) None of the above

Answer 1

Hint:The hard steel balls in the ball bearings roll thus converting sliding friction into much smaller rolling friction. The purpose of a ball bearing is to reduce friction during motion so that efficiency is increased.

Step by step solution:
If we talk about sliding friction, we can define it as resistance created by any two objects when sliding against each other. This friction is also known as kinetic friction. It depends on two variables one is material and the other is the weight of the object. Any change in the surface area in contact does not affect the sliding friction. Sliding friction is less than static friction but greater than rolling friction.

Whereas rolling friction is the force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects.

In ball bearings, hard steel balls are fixed between the two cylinders. The axle of the vehicle is fitted tightly into the inner cylinder, while the wheel is put in tight contact with the outer cylinder. When the axle rotates the steel balls and wheel rotates in the opposite direction. The two cylinders thus have smaller rolling friction instead of sliding friction.

Hence ball bearings reduce friction because they roll rather than sliding producing rolling friction.

Therefore option (A). Roll is the correct option.

Note:The use of rollers, wheels, converts sliding friction into rolling friction. As we know rolling friction is less than sliding friction, therefore by the use of rollers and wheels we can reduce the amount of force required for moving the object and so the object can be moved easily.