Harbottle Air Pressure Demonstration
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From Educational Innovations: BUY NOW Harbottle Demonstration
Harbottle Balloon Demo: a regular untied balloon remains inflated- one can even look down the neck of the balloon and see inside! Just blow up the balloon inside the bottle and then cork the hole in the opposite end- in so doing the inside of the balloon is experiencing the full force of air pressure, but the exterior of the balloon is protected from the crush of air pressure by the rigid wall of the bottle. Air pressure at sea level is 10.1 Newtons of force per each square centimeter of area (14.6 pounds per square inch). The bottle allows a pressure differential, pressure on the inside but much less on the outside of the balloon. The inside air pressure would lead to 12.5 pounds of force pushing outward on a 2 inch diameter balloon- more that enough to balance the elasticity of the rubber balloon material. Take the cork out and now both sides experience the same air pressure and the elastic force is no longer balanced. A fun demonstration reminding us that we live at the bottom of a deep sea of atmosphere!