Buoyancy in gases

An unanchored toy balloon filled with helium rises high into the sky. As it reaches higher altitudes where the outside air density decreases, what happens to the buoyant force acting on the balloon?

A rigid, sealed sphere has a total volume of \(10\text{ ft}^3\). If the weight density of the surrounding air is exactly \(0.08\text{ lb/ft}^3\), calculate the upward buoyant force acting on the sphere.

Answer = 1($)

A rising hot-air balloon will stop ascending and hover at a constant altitude when its total downward weight becomes exactly equal to the upward 1($) force exerted by the air.

A large balloon has an external physical volume of \(50\text{ ft}^3\). If the weight density of the ambient air at sea level is exactly \(0.08\text{ lb/ft}^3\), what is the total upward buoyant force exerted by the air on the balloon?

Answer = 1($)

A rigid fiberglass sphere filled with standard air weighs exactly \(12\text{ lb}\) in a vacuum. When it is placed into the outside atmosphere, it displaces a volume of air that weighs \(2\text{ lb}\). What is the net vertical force acting on the sphere, and in which direction?

"A helium-filled weather balloon will continue to rise indefinitely until it escapes Earth's atmosphere and enters the complete vacuum of outer space."