posted by roel .
a 6 kg box is stacked on top of a 15 kg box. anet leans down and pulls her elbow on the top box, exterting a force downward of -122N. what is the normal force on the top box
I am confused about whether Annette (or anet) pulls her elbow on the top box, or puts it there.
Since the top box is not going to move, the normal force on it (at the bottom, upward) equals the sum of the downward forces on it: 122N and (6kg)*g. That would be 180.8 N