Wednesday, March 13, 2013

Up, Up and Away

Hot air balloons; let’s build one and see if we can make it fly. That was the challenge given to several 7th grade students in Mr. Dehetre’s STEAM class this past trimester.

How does it work? The balloon has mass and due to gravity the balloon has a tendency to stay on the ground. To fly, the balloon must take on a force in the opposite direction that is greater than the force of gravity. Air is made up of molecules of nitrogen and oxygen. Air has mass. These molecules, when cold, move very slowly and have a tendency to stay together. When the air within the envelope is heated up this changes the behavior of the molecules. They now move faster and move apart.  Some of these molecules escape from the hole in the bottom of the envelope. As more and more molecules escape, the balloon becomes lighter allowing it to overcome the force of gravity and fly.

Taking the challenge were Sophia McGrath, Rebecca Israel, and Eliza Waterman. The girls studied a video showing how to construct and fly a model of a hot air balloon. Following the instructions, the trio built the balloon’s envelope from tissue paper. The paper was carefully cut to form gores which were then hemmed together through the use of glue sticks. Putting the balloon together was no easy task but the girls were successful with their first build. Will it fly? It sure did! Testing was done in the STEAM lab by forcing hot air into the envelope of the balloon. The girls held the balloon over the source of hot air for a good 3 or 4 minutes. Upon letting go, the balloon sailed to the ceiling.

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