Question

A person pushing a wall hard is liable to fall back. Explain

Answer 1

both the person and there wall are at rest but when person change from rest to motion the wall continues to be at rest the person fall back.

Newton's 3 law
for every action there is equal and opposite reaction

Answer 2

I think the answer to this question is Newton's 3rd law of motion every action have equal and opposite reaction and as hard we apply a force on the wall the wall also apply the same force on us but mass of is more so it doesn't displaces so there is a chance of us to fall back.