they got less popular and more simple, they came in way more colors, shapes and designs back in the 1700s than they do now.
don't worry about it
You could write about the history of hot air balloons, the physics behind how they work, different designs and shapes of hot air balloons, or personal experiences and stories from hot air balloon rides.
i like balloons
There are traditional hot air balloons, special-shaped hot air balloons (such as animals, objects, or characters), and solar-powered hot air balloons that use solar energy to heat the air inside.
Hot air balloons float because hot air displaces cool air in the atmosphere
air balloons or hot air balloons fly because they fill with a very light type of air. The air is hot air.
This may not help, but I didn't think it had ANYTHING to do with hot-air balloons...
People think that hot air balloons where made for battles.
when do hot air balloons cometo bucyrus ohio
hot air rises
olden day hot air balloons were made of heavy cotton or linen fabric and carried animals, while modern hot air balloons are made out of heat resistant nylon and carried people hope this helps if this isn't what you're looking for here are some other websites to try http://www.hotairballooning.com/faq/entry/how_do_balloons-fly-29.html or http://www.eballoon.org/history/history-of-ballooning.html these websites are really useful for projects :D
Hot-air balloons can rise up into the air because hot air is lighter, allowing it to float up into the sky.