ball of fire vs human dynamo

ball of fire and human dynamo both are nouns.

Word	Noun	Adjective	Verb	Adverb
ball of fire	Yes	No	No	No
human dynamo	Yes	No	No	No

As nouns, ball of fire and human dynamo are synonyms defined as:

ball of fire and human dynamo: a highly energetic and indefatigable person

Other synonyms of ball of fire include fireball, powerhouse.

ball of fire (noun)	human dynamo (noun)
someone whose career progresses rapidly	a highly energetic and indefatigable person
a highly energetic and indefatigable person