Can I use the Apple pencil second generation on my iPad ninth generation

No.

The first and second generation Pencil use an entirely different pairing and charging interface. 

The second generation Pencil can only be used with iPad models that have the magnetic/inductive dock that is exclusively designed for the Pencil. Charging is controlled via the iPad magnetic dock; the second generation Pencil cannot be charged using a charging mat or Qi charging solutions.

The first generation Apple Pencil uses the physical Lightning port of the Pencil and host iPad for both pairing and charging the first generation Pencil. The first generation Pencil can also be charged using an inline charging adapter and the iPad’s Power Adapter. This pencil can only be used with compatible iPad models that have a Lightning connector.

In summary, the Apple Pencil models are not interchangeable - and can only be used with the iPad that has appropriate internal hardware.

Here is the definitive compatibility list for Apple Pencil and iPad:

Apple Pencil compatibility - Apple Support

No, it is compatible with the first generation Apple Pencil, as shown in the article below.

Apple Pencil compatibility - Apple Support

Hi,

No. The iPad 9th generation only supports the 1st generation Apple Pencil. For a list detailing Apple Pencil compatibility, please see the page here.