"My cat is lying on the bed."
Translation:Mój kot leży na łóżku.
because he is there, lying, and does not move.
On with "static" verb is "na"+locative
On with movement (he is on the bed, but moving)= po +locative
on with movement from somewhere else to the bed = na+accusative
You can use „po” for "on the" when you were telling that something was moving on the surface of something (there are other uses of „po” too, but this one iis most relevant here). If something is still, you would use „na”.
Just curious - how would you translate the sentences:
My cat is on the blanket.
My blanket is on the cat.
Would it be:
Kot jest na kocu.
Koc jest na kocie?
Yes, generally yes.
However, in Polish it would probably sound better to say that the blanket is lying on the cat (Mój koc leży na kocie), and to show the 'position' of the cat - whether it's standing, lying or sitting. Mój kot stoi/leży/siedzi na kocu.