34 a 34 is the instantaneous deceleration caused by colliding with door 28 if the peak force experienced by the door is great enough to overcome the electromagnetic holding force strike plate 26 will separate from face 36 of electromagnet 20 and door 28 will have been forced open the more rigid that door 28 is the more rapid will be the deceleration of the inertial object and hence the greater the force applied to the door although the force produced by an inertial object can be lessened by making door 28 somewhat flexible there are several disadvantages to making door 28 flexible if the electromagnet is mounted at the top of the door as in fig2 then an attack against the bottom of the door may allow the bottom of the door to bend out far enough so that a crowbar or other object can be inserted between the door and the back side of the door frame the crowbar could then be used to pry the door open via the increased leveraged gained thereby the flexibility of the door would also have to be matched to the hold strength of the electromagnetic lock a flexible door would also give little protection to an inertial attack directed at the top of the door adjacent the strike plate additionally a.