Figure shows a conducting rod of negligible resistance that can slide on smooth U-shaped

Figure shows a conducting rod of negligible resistance that can slide on smooth U-shaped rail made of wire of resistance `1Omega//m`. Position of the conducting rod at `t=0` is shown. A time dependent magnetic field `B=2t` tesla is switched on at `t=0` The magnitude of the force required to move the conducting rod at constant speed 5cm/s at the same instant `t=2s`, is equal to