can someone help me with this problem A rectangular frame of conducting wire wit

Question

can someone help me with this problem

A rectangular frame of conducting wire with negligible resistance and width w is held vertically in a magnetic field of magnitude B. as shown in the figure. A metal bar with mass m and resistance R is placed across the frame, maintaining contact with the frame. Will this bar simply fall like a rock, or will something interesting happen? Let's find out... Suppose that, at some given moment, the bar is falling with speed v. What is happening to the magnetic flux through the circuit formed by the bar and the wire frame? Write an expression for the rate of change of the flux, d phi/dt. How much current flows in the circuit (in terms of v and other quantities)? hi which direction does the current flow, clockwise or counter-clockwise? Explain how this is consistent with Lenz's Law. Explain why there is a force on the bar because of that current flow, hi which direction is it? Explain how there is some speed v for which the net force on the bar is zero, and write an expression for that special v in terms of the other quantities in the problem. (Assume that friction between the bar and the wire frame is negligible.)

Explanation / Answer

a) flux is increasing

flux = B L w

dflux/dt = B w v

b) emf = dflux/dt = I R

I = B w v/R

c) getting more flux into page so we want current to make flux out of page

so counter clockwise

d) current in magnetic field so there will be a force

so right hand rule means force is up

e) F = I w B = mg

B^2 w^2 v/R =mg

v = m g R/(B^2 w^2)

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