The correct option is
D 1m/secThe rod becomes a seat of e.m.f e=Blv when it accquire the terminal velocity the resultant force on it is zero
mg−Bil=0 or mg=Bil
The equivalent corcuit is shown
i=eR1R2R1+R2
=Blv(R1+R2)R1R2
mg=BBlv(R1+R2)R1R2⇒v=mgRB2I2
e=Blv=mgRBl
P1=e2R1=m2g2R2B2l2R1=m2g2B2l2R1×R21R22(R1+R2)2
⇒(R1+R2)2R1R22=m2g2B2l2P1
⇒1R1(R1+R2)2R2=m2g2B2l2P1
Similarly,1R2(R1+R2R1)2=m2g2B2l2P2
DividingR2R1=P1P2⇒R2+R1R2=P1+P2P1
1R1(P1+P2P1)2=m2g2B2l2P1⇒R1=B2l2m2g2(P1+P2)2P1
R2=b2l2m2g2(P1+P2)2P2=(0.76+1.2)21.2×0.62×120.22×9.82
=0.3ohm
R1=(0.76+1.2)20.76×0.62×120.22×9.82=0.47ohm
v=mgB2l2.R1R2(R1+R2)=1m/sec