We are now in a position to treat the example in Sect. 8.2.1 quantitatively. Suppose q_{1} \text { is at } x_{1}=-v t \text { and } q_{2} \text { is at } y=-v t (Fig. 8.3, with t < 0). Find the electric and magnetic forces on q_{1} \text { and } q_{2} . Is Newton’s third law obeyed?