So, it makes sense to say:
The cup is on the table.
because it's on top of it. Likewise, it makes sense to say:
The cup is in the car.
because it's inside the car. But for other things, how do you know which one to use? For example:
I heard about it ___ the radio.
I like to go out ___ the weekends.
What is ___ the menu?
I read about it ___ the internet.