mas24 wrote:
Your 50mm f1.8D is the least expensive lens in its inventory. It does not automatically focus on cameras that are the D5500 or below series. These cameras don't have the internal body motors to focus the lens. The D7000 series have such motors. Perhaps you may want to pay a little more and get the AF-S lens. Otherwise you will only be able to manual focus, which isn't all bad.
The OP has an AF-D lens and a D7000, the lens should auto-focus with that camera.