1.13 A permanent-magnet DC motor with a connected inertial and friction load is depicted in Figure Pl.13. The motor armature is driven with voltage V, and the motor turns through angle 8 with torque 1: • The armature has resistance R and inductance L, and the armature current is denoted i. The mechanical load is an inertia J, and the bearings have viscous friction coefficient f The motor produces a back-emf of e = kbe and a torque of 1: = k.i , where k. and kb are constants. Determine a set