Adjustment of the eyewear frame on the user is often based on the fitting triangle. These three contact points, namely, the nose bridge and the crest of both ears support the eyewear on the face.
Facing forward, the main force that keeps the eyewear in place is friction from the nosepad on the nose. When the friction from the nosepad is adequate, friction from the temple is not required...
Friction is the primary force that keeps your eyewear from slipping down under gravitational pull. Therefore, your eyewear will start to slide down when friction is unable to keep it in place.
In engineering, friction is the force from the applied force and the friction coefficient (µ) between the two materials in contact...