[填空题]
A person exerts a force of 55 N on the end of a door 74 c h50jw ,1l8fcqannu+ dm wide. mqp lm16h. 7zhWhat is the magni7qmhz61m. lhp tude of the torque if the force is exerted (a) perpendicular to the door $m \cdot N$ (b) at a 45 $^{\circ} $ angle to the face of the door? $m \cdot N$