Question

what is the cause if friction?

Answer 1

The rough the surface the more often ''hells''. will have to push over each other and the steeper the hills will be   For most practical purposes friction is caused by the physical roughness of the surfaces involved. However, even if you make a surface perfectly smooth there's still some friction.

Answer 2

when two surfaces contact with each other then there is interlocking between both the surfaces occurs because we know that no any surface is perfectly smooth so on microscopic level friction cause due to interlocking between the two surfaces..

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