Answer: Hot air is less dense than cool air; the heated air causes the balloon to rise simply because it is lighter than an equal volume of cold air. Buoyancy is an upward force that the air exerts, and it helps hot-air balloons and blimps stay in the air. A hot air balloon uses a burner to heat up the air inside the balloon.
The statement about Charlemagne that is not true is D. He refused to acknowledge the authority of the pope interneCine and establish his own church.
World War also started after archduke Francis Ferdinand got assassinated.
