A1.0 kg copper rod rests on two horizontal rails 1.0 m apart and carries a current of 50 a from one rail to the other.
the coefficient of static friction between rod and rails is 0.60.what are the
(a) magnitude
(b) angle (relative to the vertical) of the smallest magnetic field that puts the rod on the verge of sliding?

Answer

given,

mass of copper rod = 1 kg

horizontal rails = 1 m

Current (I) = 50 A

coefficient of static friction = 0.6

magnetic force acting on a current carrying wire is

           F = B i L

Rod is not necessarily vertical

the normal reaction N = mg-F y

static friction       f = μ_s (mg-F y )

horizontal acceleration is zero

 B_w = B sinθ

 B_d = B cosθ

iLB cosθ= μ_s (mg- iLB sinθ)

       B = 0.1 T

the answer is kevlar

the force on the thing and the distance the force moves the thing