(1) As can be seen from the figure, the pulley in the figure is a moving pulley, because the moving pulley saves half of the labor, so the pulling force f is half of the gravity of the object, that is,10n; ;

(2) Because the force arm is perpendicular to the line of action of the force, the gravity direction of the hook code is vertical downward, and the lever should be balanced in the horizontal position, so the distance from the fulcrum to the hook code is the gravity arm. In order to read the value of the arm directly from the lever, the pulling direction of the dynamometer should also be perpendicular to the lever, so the pulling direction in Figure (b) is OA.

So the answer is:10; Arm of force, horizontal; OA。