If you flip a scale upside down and hook it to the ceiling, then release a helium balloon under it, such that the balloon pushes up into the scale...
A. What will the scale reading indicate? Will it really reflect the (negative?) weight of the balloon?
Edit: Will it reflect the difference in weight between the balloon and an equal volume of air?
B. Will the mechanics of how a scale operates prevent it from working in an upside down position? What if you "zero it" first?
Edit: What if the moving parts of the scale were weightless?
