We present the results of a Far Ultraviolet Spectroscopic Explorer observation of an X-ray selected knot in the Vela supernova remnant .
Spectra were obtained through the 30 \arcsec \times 30 \arcsec low resolution aperture and the 4 \arcsec \times 20 \arcsec medium resolution aperture .
O VI \lambda \lambda 1032,1038 and C III \lambda 977 are detected strongly in both spectra , and S VI \lambda \lambda 933,944 is detected weakly only in the larger aperture spectrum .
We also report the first detection of C II \lambda 1037 emission in a supernova remnant .
The spectra show the presence of two kinematic components along the line of sight - one with both low and high excitation emission centered at a velocity of -50 km s ^ { -1 } and another with only low excitation emission centered at a velocity of +100 km s ^ { -1 } .
We associate the -50 km s ^ { -1 } component with the observed X-ray knot , and find a dynamical pressure of 3.7 \times 10 ^ { -10 } dyne cm ^ { -2 } driving the shock .
We compare our results with data obtained using the Hopkins Ultraviolet Telescope at nearby locations and find that differences in the spectra imply the existence of two emitting components in the X-ray knot .
Based on the X-ray morphology seen in a ROSAT HRI image , we identify two distinct regions which can be associated with these two components whose ultraviolet emission differs dramatically .
These observations demonstrate the importance of high spectral resolution in understanding the proper physical relationships between the various emitting components in supernova remnants .