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全國熱氣球錦標賽
地方性遺產
您看過Flying
Purple Eater(會飛的紫色貪食者)？假如您在八月來到愛荷華州的印地安諾拉市，參加它的全國熱氣球錦標賽，您就有機會看到。Flying
Purple Eater是一個狀似昆蟲的熱氣球，它是這個為期三天的競賽中，100多個參賽熱氣球的其中一個。
這個熱氣球錦標賽年年舉辦，1970年剛開始時，名叫美國氣球操縱競賽。您瞭解熱氣球的運作方式嗎？氣球是輕飛行器，也就是說，充氣後，它們會比空氣輕。一旦氣球升空後，氣團或風會帶著它移動，而氣球會隨著它們的速度及方向在空中移動。
您還記得巫師是用什麼方法抵達奧茲國的嗎？他是坐熱氣球！熱氣球的駕駛員可以操控氣球的高度(即熱氣球的飛行高低)，而且可以利用方向略有不同的氣團，來改變熱氣球的飛行路線。熱氣球將一般的空氣拿來當作上升氣體。駕駛員會加熱熱氣球內部的空氣，使其比外部的空氣輕，促使熱氣球上升。當內部的空氣冷卻後，除非駕駛員再次加熱，否則熱氣球就會變重，開始下降。
Have you ever seen a Flying Purple Eater? If you go to the National Balloon Classic in Indianola, Iowa, in August, you just might. The Flying Purple Eater is an insect-like hot-air balloon -- one of more than 100 -- that takes part in this three-day event.
Held each year, this hot-air balloon competition and race began in 1970 as the first U.S. National Championship in ballooning. Do you know how hot-air balloons work? Balloons are aerostats, which means that they are lighter than air when inflated. Once a balloon is in the air, it moves with an air mass or wind, which carries it along at the same speed and in the same direction as the air.
Do you remember how the Wizard landed in Oz? He was in a hot-air balloon. The pilot of the balloon has control of the altitude (how high or low the balloon flies) and can alter its course by finding an air mass going in a slightly different direction. Hot air balloons use ordinary air as the lifting gas. By heating the air inside the balloon, the pilot makes that air lighter than the outside air, and the balloon rises. As the internal air cools, the balloon becomes heavier and descends unless the pilot adds more heat.
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關於地方性遺產
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