How many small helium balloons would you need to lift 100lbs?

Question

And no, I don't plan on strapping them to a lawn chair and going airborne.

Just curious.

Answer 1

approx. 8000,
The Mythbusters did a show on this one, here's info from that episode:

**per Episode 21 — "Ping-Pong Rescue" of Mythbusters:
"It would require such a large number of balloons (3500) to lift an average (44 lb.) 4 year old girl just a few feet off the ground"

http://dsc.discovery.com/fansites/mythbusters/mythbusters.html

Answer 2

Well, start with how much one can lift. Maybe about 1 ounce.

At that rate, it'll take 16 to pick up a pound, 160 to pick up 10 pounds, and 1,600 to lift 100 pounds.

Of course, your milage may vary.

Answer 3

Some basic physics:

Forces pulling down (weight of helium + 100 lbs of other weight) should be equal or less than forces pushing up (buoyant force of air):

Forces pulling down:
(density of helium) * (volume of helium) * (accel of gravity) +
(100 lbs) * (accel of gravity)

Forces pushing up:
(density of air) * (volume of air displaced by balloons) * (accel of gravity).

Equating the two, gravity cancels out (common factor for everything):

Volume of helium >= 100 lb / (air density - helium density)
Since I absolutely despise the english system of measure:

100 lb = 45.4kg
air density (@ 20Celsius) = 1.2 kg/m^3
helium density (@20 Celsius) = 0.166kg/m^3

Volume of helium >=43.9 m^3 (1550 cubic feet)

If you take a balloon that's about a foot in diameter and assume it to be more or less spherical, then each balloon has a volume of 4Pi(0.5ft)^3/3 = 0.5236 ft^3.

1550 ft^3 / 0.5236 ft^3 (per balloon) = 2960 balloons.

Answer 4

Standard air weight .075 lb/cubic foot, if helium weight .05, then 100 divided by (.075-.05) = 100/ .025 = 4000 cubic feet of balloons.