I used to use the 5100 for motorsports photography. It worked well. Some may feel differently, but a good place to start is to use the Shutter Priority mode. Set the shutter speed as fast as you can (assuming you are in full light), use the continuous tracking auto focus with a single spot focus. Take some practice shots, then start playing with slower shutter speeds. Once you have that down, you can start practicing panning shots (this will take some time and practice).
It is important to take some practice shots and check them prior to use. Depending on the f speed of your lens, the pictures can turn out dark when using a fast shutter speed with a slower lens. If this is the case, you can experiement turning up the ISO.
I hope that helps. Like I said, someone may have other suggestions.