Question

Two boxes, mass M and 3M are stacked on top of each other. The stack of boxes is placed inside an elevator which is accelerating upwards

Which box has a larger upward force (normal force) acting on it?

(A) The box of mass 3M

(B) The box of mass M

(C) The two boxes experience equal sized upward normal forces

(D) It cannot be determined

Answer 1

The box of mass M (the one that is on the bottom) has a larger upward force (normal force) acting on it because it must support not only its own weight but the weight of the box on top of it as well.