Question details: Is PCI-E 2.0 VGA cards compatible with PCI-E 16X slots?

Answer:

A physics card is an expansion card for computers and is used to process physics interactions in computer generated graphics. By taking over the processing of these effects, the CPU can use it's power for other tasks.

In order to find a compatible Physics card is to see on it's technical specifications if it is compatible with your interfaces available on your computer.

A physics card is built around a physics processing unit, similar to the GPU on a graphics card and contains RAM.

PCI 2.0 can be of different speeds 2, 4, 8, 12, 16, or 32x. A PCI-E 2.0 can be the same thing as a PCI-E 16X. A slot of a large physical size (e.g. x16) can be wired electrically with fewer lanes (e.g. x1, x4, or x8) as long as it provides power and ground connections required.

More about compatiblity between PCI-E versions you can find here.