If the component of the force from gravity parallel to the surface ( mg sin Î ) is greater than the static frictional force fs â `` then the body will slide down the inclined plane with acceleration where fk is the force of friction â `` otherwise it will remain stationary . Since there is no movement perpendicular to the plane , the component of the gravitational force in this direction ( mg cos Î ) must be equal and opposite to normal force exerted by the plane , N. If the remaining component of the gravitational force parallel to the surface ( mg sin Î ) is greater than the static frictional force fs â `` then the body will slide down the inclined plane with acceleration where fk is the kinetic friction force â `` otherwise it will remain stationary .