Motional Emf: Solving for Speed with E=vBL

[kiltfish]

Homework Statement

A 1.2 kg rod that has a length of 1m and a resistance of 5 ohms slides with constant speed down a pair of frictionless vertical conducting rails that are joined at the bottom. Other than the rod, the rest of the circuit is resistance-less. A uniform magnetic field of magnitude 3.0 T is perpendicular to the plane formed by the rod and the rails. Determine the speed of the rod.

Homework Equations

E=vBL

The Attempt at a Solution

I understand that B=3 and L=1
How can I solve for the other two variables with only the information I'm given? Is there some connection I just don't see? What is the relationship between resistance and induced emf, and how would I even be able to guess the emf without knowledge of voltage?

 

[gneill]

The rod and rails form a loop (a triangular-shaped loop). There is magnetic flux passing though the loop. The loop gets smaller as the rod moves downward...