A bar of mass m and resistance R slides without friction in a horizontal plane, moving on parallel rails as shown in Figure P30.49. The rails are separated by a distance d . A battery that maintains a constant emf E is connected between the rails, and a constant magnetic field B → is directed perpendicularly out of the page. Assuming the bar starts from rest at time t = 0, show that at time t it moves with a speed v = E B d ( 1 − e − B 2 d 2 t / m R ) Figure P30.49
