Is friction due to intermolecular attractive forces or repulsive ones. Since both friction and normal force are the components of contact forces, shouldn't friction be repulsive.
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$\begingroup$ why should it be repulsive ? $\endgroup$– AnkitJan 30 at 10:32
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$\begingroup$ first two paragraph of this answer of mine answers your question. physics.stackexchange.com/a/592860/271783 $\endgroup$– AnkitJan 30 at 10:34
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1 Answer
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For a force that is directed perpendicular to a surface the designations “repulsive” and “attractive” have clear meaning. Repulsive is in the outward normal direction. Attractive is in the inward normal direction.
For a force that is directed parallel to a surface those designations lose meaning. Which direction is “attractive” parallel to a surface?
Friction can neither be attractive nor repulsive since those terms do not have meaning for forces parallel to a surface.
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$\begingroup$ Ok, is it true that contact force arises due to repulsions between the electron clouds of atoms/molecules of surfaces in contact. And since normal force is repulsive, so I tried to ask that books write that friction arises due to attractive intermolecular forces, so it is due to attractive intermolecular forces or repulsive. $\endgroup$ Jan 31 at 16:32