Analysis of test questions: (1) The characteristics of plane mirror imaging are: the image formed by plane mirror is an upright virtual image with the same size, and the object image is symmetrical about the mirror surface. Axisymmetric drawing should be applied when drawing, as shown in the figure. (2) The arm of force is the distance from the fulcrum to the line of force action. When drawing a moment arm, you must first find the fulcrum, and then the imaginary vertical line of the line of action acting on the fulcrum is the moment arm, as shown in the figure.