A point charge Q of mass M is located initially at the center of the ring. When it is displaced slightly, the point charge accelerates along the x axis to infinity. Show that the ultimate speed of the point charge is v # ' 2keQ2 MR ( 1/2 An electric dipole is located along the y axis as shown in Figure P25.69. The magnitude of its electric dipole moment is defined as p # 2qa. (a) At a point P, which is far from the dipole (r .. a), show that the electric potential is V # ke p cos ( r 2 69. 67. The x axis is the symmetry axis of a stationary uniformly charged ring of radius R and charge Q (Fig. P25.67). 68.