Mechanics or what? - 3

Electricity and Magnetism Level 4

A conducting rod of mass $m$ and length $L$ is free to slide on smooth horizontal conducting rails as shown. Resistance of the resistor is R. Uniform magnetic field intensity $B$ exists through out the region and is normally inward as shown. The rod is given a initial velocity $v_o$ . Find the velocity of the rod as a function of time.

inspiration

Try my previous problem here

\large v=e^{\frac{-B^2L^2t}{mR}}

\large v=v_oe^{\frac{-B^2L^2t}{4mR}}

\large v=v_oe^{\frac{-B^2Lt}{mR}}+v_o

\large v=v_oe^{\frac{B^2L^2t}{mR}}

\large v=v_oe^{\frac{-B^2L^2t}{R^2}}

\large v=v_oe^{\frac{-B^2L^2t}{mR}}

None of these choices

\large v=v_oe^{\frac{-B^2L^2t}{3mR^2}}