Question

if there are 2 boxes, and one of them weighs 100 g and one is 50g, moving at constant velocity when an outside force is pushing on them, which one is exerting more force on the other and how can you tell?

Answer 1

second law newton\[\sum F =ma\]

Answer 2

\[F=ma\] yields that the total force must be zero on the system.The force between them must be 2x the force pushing since for no acceleration (constant velocity) there must be a co-linear force in the opposite direction. This is a system and the relative masses have no bearing on the answer. Thus the forces between are equal.