How many helium-filled balloons would it take to lift someone off the ground?
536322
a tv program showed that approximately 2600 balloons filled with helium is needed to lift 20 kg child a few centimeters of the ground. (if i remember right, of course)
23238
There was a story years ago about scientists experimenting with doing this exact thing.  They had an ozone maker under the balloon and let it off.  Can't find the article now though.\n\nSo yes, it is possible.  One theory of why its not being done would be cost - can we make enough ozone to make a difference?
978453
With Boyles law, doubling the pressure doubles the mass. No sure what the relative masses of air and helium are, but let`s say it`s 10 to 1, then 10x the pressure is what you need
530907
you should observe an initial volume 1V, and xV when the balloon had rise, at sea level atm pres. is 1 and at x is 0.8, so you do\n 1V -  1\n xV - .8\nas all inverse proportions you do the math as follows\nxV =  1\n1V    0.8   \nx = 1/0.8\nx=1.25 which means 125%\nso volume increases by a 25%
1003953
Well, the different between air and helium on the weight of the balloon is marginal, so you would expect little or no observable distance. \n\nBut in principle its not as simple as is being made out here. Think for a moment about what keeps a ball up and what brings it down. Its hit into the air at first, and then a combination of gravity and air resistance bring it down. \n\nIn a vacuum the trajectory would depend only on initial velocity, because kinetic energy and potential energy both depend linearly on mass (so it cancels). In air the air resistance is proportional to square of the speed and size but not mass.\n\nNow, about that kick. Does it give 1) constant energy independent of the mass of the ball, 2) constant speed to the ball independent of its mass \n\nIf 1) then the heavier ball will be slower when kicked, so will not go as far\n\nIf 2) then the distance will be the same in vacuum as above but the larger ball will have more energy and so will take longer to slow by drag - it will go further
90751
Take some balloons and blow them up and watch them slowly lose the air in side over a few days.  Then explain what Osmosis is.   : )   While you have the balloons out fill some with helium and show the kids how they can make their voices change.  Have your video camera ready this will be a hoot!!!
159974
Acording to the Owl... Only 3! But in the really real world it is probably more like 197! Dont know for sure but your guess is as good as mine! That would make a good science fair project!
135033
Probably won't work.  If you assume 10 billion people with an average weight of 150 lbs, the mass of the earth is about 10,000,000,000,000 (10^13) times greater.  If everyone jumped up and down, even on the same side of the Earth, it wouldn't affect the earth's momentum or motion in it's orbit.  The acceleration applied by the mass of people is just too small.  Think of it as being in the 13th decimal place(0.0000000000001), it's essentially unnoticeable.
140469
The helium balloon will continue to travel forward until it collides with the right side of the van that is now moving towards the balloon.  Once the side of the van and the balloon meet, the balloon will travel to the left.\n\nFrom the perspective of someone in the van, the balloon will APPEAR to move to the right.
739747
p1v1=np2v2\nv2 = 4/3 pi 0.15^3 = 0.014137\nn----> no. of balloons\nputting values we get n = 679.03 so approx 679 balloons.\nhope this helps
35045
They can lift up to 850 times their own weight! That's the equivalent of an average adult male carrying over 70 family-sized cars on his back!
476319
A simple answer would be that the balloon does not sufficiently prevent the helium from escaping. This can be seen if you keep the balloon around the house for a while. The "air tight" system is not so air tight as you think, and obviously some of the gases escape. If by "stops flying" you mean stops rising higher, the answer may be that the balloon has reached a great enough altitude that the pressure of the atmosphere has decreased to match the pressure of the helium contained in the balloon. This is why balloons do not continue to float infinitely off into space.
1165094
It would depend on the amount of Helium within the truck.\n\nJust because Helium is lighter (less dense) than air does not mean that it does not have mass (and thus weight).\nFor a given volume of Helium and air at the same pressure, the Helium would have less mass.  However, if one pressurized the Helium and/or had enough moles of the gas, one could actually be increasing the overall weight of the car by adding the Helium.\nIn orer to lighten the car, the idea would be to displace the surrounding "fluid" (air) but at the same time, by adding as little additional mass as possibe.\n\nAny effects of Helium upon the overall weight of the vehicle will be totally negligible using any normal amount of Helium.  One would need a small blimp's worth of Helium to have any real effect.
372306
Depends on how much helium you put into it, and how big your baloon is, and how and where you release it, and... it may well heep going up and up and up to the top of our atmosphere if you put enough in.
629282
assuming the balloons are spherical and have no mass and the temperature is about 25 C then 418 balloon might just do it.
397410
use a CD and the top of a soda bottle (both the cap and the very top) glue the cap to the CD (you need a VERY small hole in the cap) and put the balloon on the very top of the bottle, use that to blow the balloon up
950534
oxygen atoms are larger than helium atoms.\nThe helium leaches out of the balloon quicker than the oxygen.