Why are force fields used to describe magnetic force? A. Magnetic force acts between two objects that are not touching. B. Magnetic force is a form of gravity. C. Magnetic force acts between any two objects with mass. D. Magnetic force can only attract objects. tic force?

The space between two 15-in.-long concentric cylinders is filled with glycerin (viscosity = 8.5 × 10-3 lb·s/ft2). the inner cylinder has a radius of 1 in. and the gap width between cylinders is 0.1 in. determine (a) the torque and (b) the power required to rotate the inner cylinder at 180 rev/min. the outer cylinder is fixed. assume the velocity distribution in the gap to be linear.