The handle of a floor mop of mass m makes an angle with the vertical direction; see Fig. 5-50. Let k be the coefficient of kinetic friction between mop and floor and s the coefficient of static friction between mop and floor. Neglect the mass of the handle. (a) Find the magnitude of the force F directed along the handle required to slide the mop with uniform velocity across the floor. (b) Show that if is smaller than a certain angle 0 the mop cannot be made to slide across the floor no matter how great a force