physics question please help?

Question

In Figure P20.63, the rolling axle, 1.50 m long, is pushed along horizontal rails at a constant speed v = 8.00 m/s. A resistor R = 0.402 is connected to the rails at points a and b, directly opposite each other. (The wheels make good electrical contact with the rails, so the axle, rails, and R form a closed-loop circuit. The only significant resistance in the circuit is R.) A uniform magnetic field B = 0.1200 T is directed vertically downwards.

Figure P20.63
http://www.webassign.net/sercp/p20-63.gif

(a) Find the induced current I in the resistor.
A
(b) What horizontal force is required to keep the axle rolling at constant speed?
N

Answer 1

motional EMF
lets see, u have the length from rail 'a' to 'b' as as 1.5m
R is givin
so the induced current is
I = blv / R
b = .12 Tesla
v = velocity of the bar moving or wheel in your case
l = 1.5m
and
R
so plug and chug
for part B
u need to counteract the the magnetic force
so use F = ma dont remeber the equation, but im sure you'll find it