Which one to use: On vs In

Question

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:

1. I heard about it ___ the radio.
2. I like to go out ___ the weekends.
3. What is ___ the menu?
4. I read about it ___ the internet.

Answer 1

It is on the radio, on the menu, on the internet. As to weekend you find on the weekend, at the weekend, over the weekend, see Oald http://www.oxfordlearnersdictionaries.com/definition/english/weekend_1 There is a difference between BrE and AmE. BrE at the weekend, AmE on the weekend.

For learners the question what preposition to use before or after a word is always difficult. When in doubt you have to consult several online dictionaries.

Answer 2

I heard it on the radio.

I like to go out on the weekend.

What's on the menue?

I read about it on the internet.