[填空题]
A person exerts a force of 55 N on the end of a door 74 cmyw3o 4h0hi p1w ww95ia6lruvbp05 9saufkm / x4)w2wp wide. What is the magnitude of the torque if the force is exerte4 fpwal x9 avs)/5pik6wu90w ub5w2rmd (a) perpendicular to the door $m \cdot N$ (b) at a 45 $^{\circ} $ angle to the face of the door? $m \cdot N$