Q.Mention the methods used to decrease friction.

Friction is reduced mainly by lubrication, smoothing/polishing surfaces, converting sliding friction to rolling friction, and streamlining shapes to reduce fluid drag.

Friction arises largely from the interlocking of microscopic irregularities between two surfaces in contact, so most methods to reduce it aim to minimise this interlocking or replace one type of friction with a less resistive type. Common methods include:

1. Lubrication: Applying oil, grease, or other lubricants between two surfaces creates a thin film that keeps the solid surfaces from directly touching each other, drastically reducing friction. This is used in machine parts, engines, and hinges.

2. Polishing surfaces: Smoothing out the irregularities of contacting surfaces (e.g. by polishing) reduces the interlocking between them, thereby reducing friction.

3. Using ball bearings or rollers: Rolling friction is generally much smaller than sliding friction. Placing ball bearings or rollers between two surfaces that need to move relative to each other (e.g. in wheels, machine axles) converts the high sliding friction into much lower rolling friction.

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