How does a hot air balloon stay in the air?
Why do you think that the explanation given or the airplane remaining in the air will not account for the buoyancy of a balloon? Since we have learned that air has weight we may compare the floating of objects in air with the floating of objects in water. You know from experience that objects like iron and stones, that are heavier than water, will sink while cork and wood, which are lighter than water, will float. The same is true of things in the air. Cork and wood and most things we know of are heavier than air and will not float in it. A balloon, however, is lighter than air and therefore will float in it. We know that air pressure is exerted in all directions. The air under the balloon, therefore, is pushing it upward and the air above it, is pushing it downward. If the balloon weighs the same as air it will not be pushed either upward or downward. If, however, the balloon weighs more than an equal volume of air, will the downward or upward pressure be greater?
