(a) Charge qA is at rest at the origin in system S; charge qB flies by at speed v on a t...

(a) Charge q_A is at rest at the origin in system S; charge q_B flies by at speed v on a trajectory parallel to the x axis, but at y = d. What is the electromagnetic force on q_B as it crosses the y axis?

(b) Now study the same problem from system which moves to the right with speed v. What is the force on q_B when q_A passes the axis? [Do it two ways: (i) by using your answer to (a) and transforming the force; (ii) by computing the fields in and using the Lorentz force law.]