A conductor bar with mass m and length L slides over horizontal rails that are connected to a voltage source. The voltage source maintains a constant current I in the rails and bar, and constant, uniform, vertical magnetic field `vecB` fills the region between the rails (as shown in Fig.)

If the bar has mass m, find the distance d that the bar must move along the rails from rest to attain speed v.

Options

A. `(3v^2m)/(2ILB)`
B. `(5v^2m)/(2ILB)`
C. `(v^2m)/(ILB)`
D. `(v^2m)/(2ILB)`

Answer

d

Explanation

`F=ILB`, to the right.
`v^2=2ad implies d=(v^2)/(2a)=(v^2m)/(2ILB)`