Answer
As the balloon rises in the air, the surrounding air pressure gradually decreases. As a result, the balloon expands as it rises. If the balloon was not underinflated at ground level, when it rose into the sky, the expansion of the balloon would cause it to burst.
Work Step by Step
As the balloon rises in the air, the surrounding air pressure gradually decreases. As a result, the balloon expands as it rises.
If the balloon was not underinflated at ground level, when it rose into the sky, the expansion of the balloon would cause it to burst. By underinflating the balloon at ground level, the balloon can safely expand as it rises into the sky.
