Question

Assertion :Polishing of a surface decreases the coefficient of friction up to a certain limit; beyond which it increases. Reason: The friction force arises in parts, as one peak blocks the motion of another peak from the opposite surface and in part from chemical bonding of two opposing peaks as they come in contact.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Friction arises due to molecular adhesion, more precisely due to electrostatic forces at the surface.The roughness of the surface plays a role when the hills and valleys of a surface helps to lock the other surfaces and avoid motion. Molecules exerts strong attractive forces on each other which eventually increase the surface friction.