Suppose you were to fill a balloon with air then let go of it withoutntying it closed. What causes the balloon to fly away?

When a balloon is inflated, the pressure inside the ballon is greater than the pressure outside the balloon. When let go of (or when the balloon is open), the air is released as there is no long a difference in pressure between outside the balloon and inside the balloon. This results in a force in the opposite direction due to the escaping air that provides the force, which causes it to fly away!

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jupiter is the largest planet in our solar system, having a mass and radius that are respectively, 318 and 11.2 times that of earth. suppose that an object falls from rest near the surface of each planet and that the acceleration due to gravity remains constant during the fall. each object falls the same distance before striking the ground. determine the ratio of the time of fall on jupiter to that on earth.