GNRCustoms.......With a quality camera, be it digital or the 'old' film type, the sharp focus subject (drag car!!), and blurred background depends on shutter speed, as Jon said, but also on 'tracking', or 'panning' with the subject. The basic (digital) camera I have (FujiFilm FinePix S 5800, 8Mp, 10x optical zoom) is pretty much fully automatic - I believe you CAN do some settings manually, I'm just old and lazy, not that fussed - and I have managed to grab a couple good shots (and a LOT of rubbish ones) of fast moving objects with it. Tip one is to pick your spot, my shot in the previous post (Tommy johnson Jr) I aimed across from the spectator bank to a point I wanted to take the shot at, gently pressed the shutter release to 'set' the focus and such, then holding that in position, went back to aim on the car at the startline. When they took off I 'tracked', or 'panned' with the car, then at the moment I had preselected, fully depressed the shutter release to get the shot. The 'technical' details on this shot: ISO 64, 1/210, F4.5, no flash, auto white ballance, standard 'film', and the 'fine' setting for the 8Mp setting (gibberish to most, I guess). These sort of digital cameras are notorious for their 'SLOW' reaction in firing the shutter and grabbing the shot. This was an old trick from the long-gone days of 'REAL' film and 'real' cameras (21st Century, bummer!), the FULLY MANUAL ones at that. Okay, not every shot will come out perfect, but hope the 'half cocked' trick will help. Certainly improved several of my friends' shots when they went digital and found their shots were all of the beautiful black surface of the dragstrip, not the car or bike they were after. Also improved the focus on the ones they did get, too. The more 'professional' (read expensive) a kit you have, the better the shot should be anyhow. Like the old story goes, though, practice makes perfect. At least with some experimentation you can see INSTANT results with a digital.....that's the REAL beauty of them, no waiting for the D&P*, then feeling gutted you missed the shot, or some geek got their head right in the way. Best of luck, hope the tips help.
(*Dissapointment and Perseverance)