Difference between 'have to' and 'must' ?
I really can't understand the difference between 'I have to' and 'I must'. I've always though that 'must' is for strictly permissions, such as 'don't throw away paper, you must recycle it' ecc., and 'I have to' for permission too, but not so strictly.
For example, are these sentences correct?
I have to go now, my train leaves at 17pm.
I must read this book for next week.
I should study for the exam, but I'm not feeling good.
You have to buy something to eat on the way home.
I have to wash all these dishes, but now I'm going to watch some Tv.
I have to take out the dog.
You must come back in 5 minutes, or I'll go without you.
So, where is it necessary to use 'must'? And where not?