Halliday, Resnick & Walker — Magnetic Fields: Problem 32

32 In Fig. 28-35, a metal wire of mass $m = 24.1 \text{ mg}$ can slide with negligible friction on two horizontal parallel rails separated by distance $d = 2.56 \text{ cm}$. The track lies in a vertical uniform magnetic field of magnitude $73.5 \text{ mT}$. At time $t = 0$, device G is connected to the rails, producing a constant current $i = 9.13 \text{ mA}$ in the wire and rails (even as the wire moves). At $t = 61.1 \text{ ms}$, what are the wire's (a) speed and (b) direction of motion (left or right)?