Magnetic field, current, and a slide wire

AI Thread Summary
The discussion revolves around a physics problem involving a U-shaped conducting rail in a magnetic field and a slide wire that can move vertically. The user initially struggles to determine the terminal velocity due to confusion over the relevance of the slide wire's mass and the absence of given electromotive force (V_emf). Key equations mentioned include the relationship between current, resistance, and magnetic force. The user realizes the importance of the vertical orientation of the rail, which clarifies the problem. Ultimately, the user expresses relief after understanding the question better.
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Hi, I really need help with this question.

Here's the question:

"The figure shows a U-shaped conducting rail that is oriented vertically in a horizontal magnetic field. The rail has no electric resistance and does not move. A slide wire with mass m and resistance R can slide up and down without friction while maintaining electrical contact with the rail. The slide wire is released from rest."

"Determine the value of a terminal velocity if l = 25.0 cm, m = 10.0 g, R = 0.100 ohms, and B = 0.550 T."

I know that V_emf = vlB
I = V/R = vlB/R
If I can find I, then I could determine v. The problem is they don't give V_emf, so I cannot find I. and I have no idea why would they give the mass for, when generally for this type of problem they don't. Any hints would be greatly appreciated.
 

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F = IlB
P = Fv = (v^2)(l^2)(B^2)/R

I just don't see how could the mass be relevant to this problem. If it was a particle then may be I could use the mass to do something with the circular motion but this just doesn't make sense. Please help.
 
I think I might get it now, I just didn't read the question carefully and miss the "vertical part".
 
:eek: OK, I got it, still cannot believe I could miss the keyword "vertical". Thanks and sorry for this. Please don't get mad at me. I'm going to sleep now at almost 8 A.M. :zzz:
 
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