Hot Air Balloons
Experiment & Video
In this video, you'll be using your garbage bag, hair dryer, and duct tape to convert an ordinary trash bag into a floating masterpiece.
Hot air balloons that took people into the air first lifted off the ground in the 1780s, shortly after Leonardo da Vinci’s plans for the ornithopter took flight. While limited seating and steering were still major problems to overcome, let’s get a feeling for what our scientific forefathers experienced as we make a balloon that can soar high into the morning sky.
Shake out a garbage bag to its maximum capacity. Using duct or masking tape, reduce the opening until it is almost-closed leaving only a small hole the size of the hair dryer nozzle. Use the hair dryer to inflate the bag, heating the air inside, but make sure you don't melt the bag! When the air is at its warmest, release your hold on the bag while at the same time you switch off the hair dryer. The bag should float upwards and stay there for a while.
Troubleshooting: This experiment works best on cold, windless mornings. If it’s windy outside, try a cool room. The greater the temperature difference between the hot air inside the garbage bag versus the cold, still air, the faster the bag rises. The only other thing to watch for is that you’ve taped the mouth of the garbage bag securely so the hot air doesn’t seep out. Be sure the opening you leave is only the diameter of your hair dryer’s nozzle.
What's Going On?
The higher pressure is generated inside the bottle when you squish it. Because air is a gas, it's also compressible, which means you can pack the same volume of air into a tighter space. When you decrease the volume, you increase the pressure. Since higher pressure always pushes, the rocket feels a push as soon as the bottle collapses down, which moves the rocket forward.
Now it's your turn – go have fun!
I look forward to sharing more fun, excitement and learning with you in our next issue.
Talk soon,
Aurora
P.S. If you'd like to experience one of my free educational (and FUN) online science classes, so you can see first hand how your kids can enjoy learning science... then simply register for my next class by clicking the link below...
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