Question

WHAT ARE THE FORCE ACTING ON YOUR BAG WHEN YOU LIFT IT ON YOUR SHOULDER . WHICH FORCE OUT OF THESE IS RESSPONSIBLE FOR ITS POSITION?

Answer 1

The forces acting at the point of contact of the bag and your shoulder are: gravitational force of the bag in downward direction and normal force by the shoulder on the bag in the upward direction.

The normal force applied by your shoulder will keep the bag in its position. An increase in normal force will push it upwards and a decrease in normal force will let the bag come downwards. So, the normal force is responsible for the position of the bag.