What Makes a Helium Balloon Rise?
Helium balloons are popular children’s toys because they rise into the air, needing to be tethered with a string to keep them from flying away. Balloons blown up with breath, on the other hand, don’t have this property. This is due to a difference in buoyancy. Helium balloons’ behavior is analogous to things that float in water, such as ice cubes and life preservers. Buoyancy Helium balloons rise because of the buoyancy force created by the surrounding air. Buoyancy is the tendency of fluids to seek their lowest point. As a result, they push up anything less dense. An object in a fluid will keep rising until the surrounding fluid has the same density as the object; that is, the fluid displaced is of the same mass as the object that the fluid is supporting. If the fluid is a liquid, this equality may be achieved when a certain proportion of the object pokes above the fluid’s surface. Air Has Weight Balloons exert a compressive force on their contents because they want to return to their
