"ndicular to the center line of the socket contact, (X.sub.1, and Y.sub.1 are thecoordinates of a boundary point 95 between the contact portion 96 and the spring portion 94, .mu. is a dynamic friction coefficient between the contact portion 96 and the parallel portion of the pin contact, and A' is a constant determined by X.sub.1,Y.sub.1 and .mu..Further, the linear portion 99 is formed by replacin" . . . .