Which of the following is NOT a plain bearing type?

• A. Journal Bearings
• B. Thrust Bearing
• C. Linear Bearing
• D. Ball Bearing

Answer: (D)

Plain bearings are sliding bearings where the shaft or journal moves against a bearing surface with little to no rolling elements between them. They rely on lubrication to minimize sliding friction, and examples include journal bearings, which are sleeves around a rotating shaft, and thrust bearings, which provide axial support with sliding surfaces. Linear bearings can also be plain types when they use a sliding sleeve or bushing for linear motion, though there are rolling-element linear bearings as well. Ball bearings, on the other hand, use rolling elements—balls—between inner and outer races to reduce friction and carry loads. Because of these rolling elements, they are not plain bearings. So the choice that is not a plain bearing type is ball bearing.