Question

a person pushing a wall hard is liable to fall back, give reason

Answer 1

due to Both the person and there wall are at rest but when person change from rest to motion the wall continues to be at rest and the wall also pushes back

Answer 2

according to Newton's third law of motion:if one body exerts a force on another body then the second body exerts an equal and opposite force on the first body.

here,force applied on second body by first body is known as action and force applied on first body by second body is known as reaction.

So here in this case,the force applied by man on wall is action and the force applied by wall on man is reaction.

but here, it is exceptional, the person will not get any such reaction force that the person can fall.