How Does Adding Mass Affect Normal Force?

[mystmyst]

I just made up this question to understand how normal force works:

Let's say mass A = 20 kg and it's on a flat surface. The normal force = 20g

But what happens when you put mass B on top of mass A?

mass B = 10kg

Does mass A have the same normal force, or does the normal force equal 20g + 10g

And does mass B have it's own normal force reacting on mass A which would equal 10g?

 

[Delzac]

The force acting on block A due to the ground would be 30g. The force that block A acts on block B is 10g.

 

[mystmyst]

Thanks for your quick response!