TELEPHONE DIAPHRAGMS. 



465 



(0 of the particle in the orbit. It is evident that (1) diminishes with 

 increase of co, while (3) augments. The vector diagram of Figure 25 

 represents the system of forces acting on the particle for the particular 

 value coo, at which the two reactive forces (1) and (3), of resilience and 

 inertia respectively, equate and cancel. The direction of reference 

 OD, or standard phase, is the vector of instantaneous velocity x, at 

 the moment selected. Then OA represents force (1) to magnitude and 

 phase, or the vector reactive force of resilience tending to bring the 

 particle to the center O, Figure 24. The equal and opposite reactive 

 force OB, of inertia, tends to move it centrifugally away from O, 



FIG.Z4- 



p '«-j"x 



Fio.ZJ 



C-«- 



'^y-i-D 



Fig. 27 



Figs. 24, 25, 26, 27. — Diagrams of Motional Equilibrium. 



in the direction of instantaneous displacement x, Figure 24. The force 

 OC is directed opposite to the instantaneous velocity. The impressed 

 vector rotating force F = OD, is directed in phase with this velocity. 

 It balances the retarding force OC. The active forces OD and OC 

 therefore cancel, while we have seen that the reactive forces OA and 

 OB also cancel ; so that the system will retain a steady state of motion, 

 with the angular velocity wq. The power put into the s^'stem by the 

 impressed force is Fx ergs per second, and this is equal to the dissipa- 

 tory output of the system rx"^, through the action of the frictionally 

 retarding force. 



