Answer: number 1: Because the air in the balloon has less mass per unit of volume than the air in the atmosphere, it would be lighter than the air it was displaced, so the buoyant force would lift the balloon up.
2:Hot air balloons are based on a very basic scientific principle: warmer air rises in cooler air. Essentially, hot air is lighter than cool air, because it has less mass per unit of volume. A cubic foot of air weighs roughly 28 grams (about an ounce).
3: Science tell us that hot air rises, and as the air is heated inside the balloon it causes it to rise upwards (because it is lighter than the cooler air on the outside). When the pilot needs to bring the balloon down again, he simply reduces the temperature of the air inside the balloon causing it to slowly descend.
Step-by-step explanation:
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