Impending Motion An object sits on a plane surface which can be tilted. As we tilt further from the horizontal, the force of gravity begins acting parallel to the surface (Fgx) as well as perpendicular to it (Fgy). The force of gravity acting perpendicular to the surface (Fgy) creates the normal force (n) from the surface, pushing back up against the object. The maximum force of static friction (FsMAX), is the product of the normal force (n) and mu, the coefficient of static friction. As we tilt, FsMAX, which stops the object sliding away, gets smaller as Fgx, the force pulling it down the slope, gets larger. When FsMAX = Fgx, the object will be in a state of impending motion, just about to slide. Find the angle at which the object will slide for different values of the coefficient of static friction, mu.