Wednesday, March 3, 2010
So Jane recently saw the movie UP, and that got her to thinking. Is it possible to lift a real house with helium balloons?
As it happened, the homeschool Science Fair was just around the corner, so she decided to pursue this as her project. She would try to determine the number of helium balloons needed to lift a small, wood-sided (foundationless) house completely off ground level.
She started her project by contacting a home-demolition company online. They told her that a two-story house with wood siding like the one she described would weigh about 60.5 pounds per square foot, or 121 pounds per square foot of footprint.
We evaluated pictures of the house from the movie and estimated that the house in UP was about 800 square feet, with about a 400 square foot footprint.
She did her math to find that the house should weigh about 48,400 pounds. An online website helped her convert that to 21,954 kilograms.
Using new pennies, which have a mass of 2.5g each, and our balance, she found the mass of several small items around the house. Then she experimented to see how many balloon units (one balloon unit = 1 12-inch latex balloon, filled with helium and tied with a 3-foot segment of nylon kite string) it took to lift each of those small objects: a toy Jeep, a banana (a la Goodnight Gorilla), a toy football.
Then came the big experiment. She would estimate the number of balloon units needed to lift the model house she was using for her project: a 2-pound, 5 ounce (1,049g) plastic dollhouse in a style similar to Mr. Frederickson's house in UP.
I let her make her estimate based on her own interpretation of the facts gathered from floating the other objects. Her prediction was that it would require 180 balloon units to lift the toy house.
We inflated and tied on balloons in clusters of 10. At 80 balloons, it was clear that this house wasn't budging.
We kept trying, but our helium supply ran out at 208 balloon units. The house still would not clear the ground, but the front corners were just beginning to lift, and if she tossed it into the air, it would hang there for just a fraction of a second before dropping back down with a serious thud.
After looking at her math again, she revised her estimate to 230 balloon units, but we were unable to test it. She will be presenting at the Science Fair on Friday, stating that she still believes her theory is plausible, but that she was not able to prove it at this time.
Oh, well--I guess we'll be in for a repeat in the future. I wonder if there's grant money available for this kind of research.