2. To see how these calculations are done, use the graph in Figure 27.2b to determine the radial velocity, v, at a radius, r, of 9 kpc from the center of the galaxy. v = km/s 200 NGC 2742 @ 100 i = 8 o0 2 & o 100 200 (a) -8 0 4 8 Distance from center (kpc)