Needle bearings are characterized by which feature?

• A. Bearings with cylindrical rollers that are small in diameter relative to their length.
• B. Bearings that use magnetic levitation.
• C. Bearings with spherical balls.
• D. Bearings designed for high-speed liquid cooling.

Answer: (A)

Needle bearings are defined by their slender, long rollers. The rollers are cylindrical and have a small diameter relative to their length, giving a high length-to-diameter ratio. This design lets the bearing carry heavy radial loads in a very compact space, because the long rollers distribute the load over a larger contact area and reduce bending stress on the shaft.

Other descriptions describe different concepts: magnetic levitation bearings use magnetic forces to support movement, which isn’t what needle bearings rely on; bearings with spherical balls refer to ball bearings; and high-speed liquid cooling describes cooling methods or special bearing designs, not the defining shape of the rollers.