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Observer 2 and a subject A with mass m are falling down from a building

Observer 1 is standing on the ground to observe the motion of these two objects

Ignore the air resistance

In observer 1,he sees the force acting on A

=ma(A,1)

=m[a(A,2)+a(2,1)]

In observer 2,he sees the force acting on A

=ma(A,2)

Obviously a(A,2)=0,but this doesn't make sense

So, we introduce pseudo force f=-ma where a is the acceleration of the frame

The problem is here,which equation should I add the pseudo force into?

I don't know the above assumption is correct or not,please check!