Which of the following is not an effective method to reduce friction and increase machine efficiency?

• A. Proper lubrication
• B. Using high-quality bearings
• C. Roughening contact surfaces
• D. Ensuring proper alignment

Answer: (C)

Minimizing resistance at the contact interfaces and keeping motion smooth and properly oriented are what boost efficiency. Lubrication creates a film between surfaces, dramatically reducing direct metal-to-metal contact and lowering friction. High-quality bearings are designed for low friction through precise manufacturing, smooth bearing surfaces, and appropriate materials, which also helps reduce wear. Proper alignment ensures loads are carried evenly, preventing binding, uneven contact, and extra sliding resistance that would waste energy. Conversely, roughening contact surfaces increases asperity interlocking and raises the real contact area, which raises the friction coefficient, speeds wear, and generates more heat. This undermines efficiency, so roughening surfaces is not an effective method.