Anti friction bearings are divided into two general categories. Which pair represents these categories?

• A. Ball bearing and roller bearing
• B. Plain bearing and ball bearing
• C. Magnetic bearing and air bearing
• D. Spherical bearing and thrust bearing

Answer: (A)

Anti-friction bearings work by using rolling contact to carry loads, which greatly reduces friction compared to sliding contact. The two general families are those that use balls as the rolling elements and those that use rollers. Ball bearings have spherical balls between the races and are versatile for various loads, while roller bearings use cylindrical or tapered rollers and excel at handling higher radial loads. Together, ball bearings and roller bearings cover the main rolling-contact categories of anti-friction bearings.

Other options don’t fit the broad classification: plain bearings rely on sliding contact and aren’t anti-friction in the rolling-sense; magnetic and air bearings are specialized non-contact types, not the standard rolling-element families; spherical and thrust refer to particular bearing designs or load directions rather than the overall two-category split.