physics question please help mee?

Question

A 0.220 kg metal rod carrying a current of 10.0 A glides on two horizontal rails 0.520 m apart. What vertical magnetic field is required to keep the rod moving at a constant speed if the coefficient of kinetic friction between the rod and rails is 0.100?
T

Answer 1

m=.220kg, mu_k=.100, L=0.520m, I=10A, Ffr=Fn*mu_k=mg*mu_k
Ffield=current*length*B-field*sin(angle) (F=ILB*sin(angle))
Ffr=Ffield
Ffr=(.220)*(9.8)*(.100)=.2156N
Ffield=.2156N
.2156=10*.520*B
B=.0415T

You know that the force of friction has to be equal to the force by the magnetic field so then you set them equal to each other. After you find the frictional force then use the equation F=ILBsin(angle)
and solve for B. sin(angle) isn't in the work because the sin of 90 degrees is 1. Just check my work but that's the way to go about it.