Props for going the extra mile for science!![]()
While at it, we may as well complain that the 5 foot iPad models on display arent real.
Helium has a lifting force of about 1 gram per liter. (source)
A typical amusement park balloon holds 14 liters of Helium.
The 11in MBA weighs 1.06Kg (1060g), so you'd need about ~76 balloons.
The 13in MBA weighs 1.32Kg (1320g), so you'd need about ~95 balloons.
This is assuming the balloon itself and string are negligible in weight... so you may wanna throw in some extra balloons![]()
if the balloon was real would it really be able to lift that air?
It's exactly so, for further reading one can read this - http://cr4.globalspec.com/thread/21168/How-much-helium-do-one-need-to-lift-1KgSince the Air weighs 1.06Kg and as another poster mentioned helium has a lifting force of 1gram/Liter, it's a very straight-forward bit of math. 1060grams=1060 Liters of Helium (plus change for balloon and string mass). That is equal to a cube of about 1.02 meters on all sides, or a spherical balloon 1.27 meters in diameter.
It probably could fit in a window display, but I think the effect would be lost.![]()