a) A thin, uniform rod has a length of 0.30m, mass of 0.15kg, and is attached by a hinge at the point P. A uniform magnetic field B = 0.55T is directed perpendicular to the plane of the rod. A current of I=3.6A flows through the rod causing the rod to remain in mechanical equilibrium at the angle above the horizontal. Find the angle.
b) The coil of a dc motor contains 550 turns and has an area per turn of .012m2. The magnetic field is .049T and the current in the coil is 0.1A. A brake shoe is pressed perpendicularly against the shaft to keep the coil just from turning. The normal force acting through the shoes is 4.3N. The radius of the shaft is 0.015m. What is the value of the coefficient of static friction?