Question

Which methods reduce friction?

increasing speed
lubricating surfaces
using sticky materials
increasing surface roughness

Answer 1

Lubricating surfaces.

Reason: Lubricants create a film between surfaces so they don’t contact directly, greatly reducing friction.

Why the others are wrong:
- Increasing speed: frictional force for dry sliding is generally independent of speed (or can even increase for fluids due to drag); it is not a reliable way to reduce friction.
- Using sticky materials: increases adhesion and therefore increases friction.
- Increasing surface roughness: typically increases friction by increasing interlocking and contact area.