solid ground vs physical object

solid ground and physical object both are nouns.

Word	Noun	Adjective	Verb	Adverb
solid ground	Yes	No	No	No
physical object	Yes	No	No	No

As nouns, physical object is a hypernym of solid ground; that is, physical object is a word with a broader meaning than solid ground:

solid ground: the solid part of the earth's surface
physical object: a tangible and visible entity; an entity that can cast a shadow

Other hypernyms of solid ground include object.

solid ground (noun)	physical object (noun)
the solid part of the earth's surface	a tangible and visible entity; an entity that can cast a shadow