11. The current density in a cylinder of radius R is given by J = Kr, where K is a constant. What is the magnetic field within the cylinder?Ans：___(15)____

(a).Suppose that the cylinder is sliding without rolling down the smooth inclined face of the wedge, and the wedge is free to move on a horizontal plane with friction. How far has the wedge moved by the time the cylinder has descended from a rest a vertical distance h?Ans：___(1)____