Task: Text Categorization
Input (English): Two kinds of this force cause inconsistencies in rigid-body dynamics in the Painleve paradox. The Tomlinson model describes this force at the atomic level, and this force causes buildup of electrostatic charge in the triboelectric effect. The independence of this force from area of contact is described by Amonton's second law, and for a block on an inclined plane, the static coefficient of this force is equal to the tangent of the angle. For 10 points, name this force perpendicular to the normal force, which resists the motion of objects sliding against each other.
Output (English): Science