Question

A 70 kg man pushes a 50kg man with 50n force.by what force a 50kg man push back

Answer 1

According to Newton's third law of motion:

For every action there is an equal and opposite reaction.

When the 70kg man pushes the 50 kg man using 50N:

The force applied by the 70 kg man is the action force.

The force exerted by the 50kg man is the reaction.

This reaction is equal and opposite to the action :

The reaction is thus 50 N