ne 2 FIGURE 23-2 Problem 34. 35. (II) A flat ring of inner radius R1 and outer radius R2, Fig. 23-30, carries a uniform surface charge density o. Determine the elec- tric potential at points along the axis (the x axis). [Hint: Try substituting variables.] FIGURE 23-30 Problem 35. 36. (II) A total charge Q is uniformly distributed on a thread of length l. The thread forms a semicircle. What is the potential at the center? (Assume V = 0 at large distances.) 37. (II) A 12.0-cm-radius thin ring carries a uniformly distributed 15.0 MC charge. A small 7.5-g sphere with a charge of 3.0 JC is placed exactly at the center of the ring and given a very small push so it moves along the ring axis (+ x axis). How fast will the sphere be moving when it is 2.0m from the center of the ring (ignore gravity)? 38. (II) A thin rod of length 20 is centered on the x axis as shown in Fig. 23-31. The rod carries a uniformly distributed charge Q. Determine the potential V as a function of y for points along the y axis. Let V = 0 at infinity. FIGURE 23-31 Problems 38, 39, 40, and 53