Interested in Language
Do we usually know someone and know about something?
Do you know that?
I know that guy.
My new car is pretty fast, which is logical because of its 150 hp.
I know (about) your car's hp.
Once Raymott said, "In English we usually know about problems."
So are there differences between problems and other things?
You've asked a difficult question. I'm not going to try to answer it, but I would like to point out that you can also "know of someone/something."
I know of no one who could answer that question.
A: Do you know Obama Barack?
B: No, but I do know of him.
He knows of the dangers involved in this enterprise.