Motional EMF -- problem 7.7 in Griffith

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Pushoam
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Homework Statement


Diagram of a metal bar of mass m sliding to the right at speed v on two parallel rails a distance l apart, with resistor R connected across the rails on the left and a magnetic field region between them.

I need help in solving (c) and (d).

Homework Equations

The Attempt at a Solution


Since the force acting on the bar is Magnetic force and magnetic force does no work, the speed of the bar will remain same i.e. v0.
Question (d) is not making sense to me.
 
Pushoam said:
Since the force acting on the bar is Magnetic force and magnetic force does no work, the speed of the bar will remain same i.e. v0.
Energy is being dissipated in the resistor. Where is this energy coming from?
 
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