Statics Reference

Current page:

    Friction

    Friction is a force that resists the movement of two contacting surfaces sliding relative to each other. Frictional forces act tangential to the surface at the point of contact and act in opposition to the possible or existing motion between the surfaces.

    Limit on friction force magnitude.
    $$ F \le \mu F $$

    Variables \( F \) and \( N \) are the magnitude of the friction for \( \vec{F} \) and the normal force \( \vec{N} \), and \( \mu \) is the coefficient of friction.

    Static Friction

    Examples of coefficients of static friction:
    SystemStatic friction \(\mu_s\)
    Rubber on dry concrete1.0
    Wood on wood0.5
    Steel on steel0.6
    Shoes on wood0.9
    Shoes on ice0.1
    In TAM 210/211, we will focus on dry friction. Dry friction occurs between two surfaces with no lubricating fluid between them. Static friction is the friction between two bodies when there is no movement between them.

    Tipping vs. Slipping

    tipping vs. slipping

    To solve for X (the location of the normal force), one can write the equations of equilibrium.

    Note: See below for an explanation of why the normal force does not act at the center of mass of the box.

    Note explanation