3. A metal rod of mass m = 250 g and length L = 50 cm is free to slide on two parallel, frictionless horizontal metal rails as shown in the figure below. The rails are connected at one end so that they form a closed electric circuit with the rod. The rod and the rails have a combined resistance of 2 . A uniform magnetic field B, perpendicular on the plane of this circuit and oriented vertically upward, is decreasing at a rate of 0.3 mT/s. At time t = 0 s, the magnetic field has a strength of 15 mT, and the rod is at rest at 150 cm from the connected end of the rails. (a) (b) E B(t) Describe the forces acting at t = 0s and thereafter. Derive an expression for the acceleration of the rod at t = 0 s in terms of the given quantities.

3. A metal rod of mass m = 250 g and length L = 50 cm is free to slide on two parallel, frictionless horizontal metal rails as shown in the figure below. The rails are connected at one end so that they form a closed electric circuit with the rod. The rod and the rails have a combined resistance of 2 . A uniform magnetic field B, perpendicular on the plane of this circuit and oriented vertically upward, is decreasing at a rate of 0.3 mT/s. At time t = 0 s, the magnetic field has a strength of 15 mT, and the rod is at rest at 150 cm from the connected end of the rails. (a) (b) E B(t) Describe the forces acting at t = 0s and thereafter. Derive an expression for the acceleration of the rod at t = 0 s in terms of the given quantities.