3. (1 point) An object with weight W is dragged along a horizontal plane by a force acting along a rope attached to the object. If the rope makes an angle 9 with the plane, then the magnitude of the force 18 pW _ psin(9) + cos(9) Where ,u is a positive constant called the coefcient of fric- tion and where 0 S 8 g n/Z. Find the value for ma which minimizes the force. Your answer may depend on W and p, but use \"u\" instead of ,u when entering your answer. F ma: 4. (1 point) A painting in an art gallery has height h and is hung so its lower edge is a distance d above the eye of an observer (as in the gure). How far from the wall should the observer stand to get the best view? (In other words, where should the observer stand so as to maximize the angle 8 subtended at his eye by the painting?) (Your answer may depend on h and d.) 4