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How does lift, gravity, thrust and drag affect a hot air balloon?
Lift is created by the difference in air pressure inside and outside the balloon. The hot air inside is not as dense as the cool air outside, and since the mass of hot air produces enough upward lift to overcome gravity, the balloon will rise.
When it comes to drag and thrust, the balloon isn't moving fast enough to be bothered by the drag, and there's no engine producing thrust, so they have little effect on hot air balloons.