Friction between two surfaces is caused by:
AGravity acting at the contact point
BMagnetic attraction between atoms
CInterlocking of irregularities on the two surfaces
DAir pressure between the surfaces
Answer & Solution
Correct answer: C. Interlocking of irregularities on the two surfaces
Even surfaces that look smooth have many tiny bumps and depressions. When two such surfaces are pressed together, the bumps lock into one another. Moving one surface requires force to overcome this interlocking — that resistance is friction.
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 is caEven surfaces that look perfectly smooth — like glass or polished steel — have a large num