These are easier to work on in my opinion. First, notice how the cable or rod activates the brake by pulling on the arm. Kick the arm with your foot or whack it with a hammer back away from the cable, and see if that frees up the brake. If so, there may just be some rust in there causing it to stick, and you will need to service them when you get home.
If they are still hung up, you can pretty easily take them apart to see if there is major corrosion, or you can adjust them if the cable is too tight. Here is how to do that:
Remember its also possible that your bearings have seized. These usually fail only after many miles of whining and protesting, but if you have been ignoring these signs, they might have seized. Here is how to replace them:
