Amazing anti-gravity water trick
A great, simple experiment to surprise both children and adults
- glass bottle with water;
- piece of gauze (about 5 * 5 cm);
- thin rubber band;
Cover the neck of the glass bottle filled with water with a piece of gauze. Fasten the gauze in place with a rubber band. Cover the opening with one hand and turn the bottle upside down. Remove your hand. Notice that the water doesn't leak out! Slip some matches between the holes in the gauze – the water still stays put!
When we invert the closed bottle, a pressure equal to the sum of the atmospheric pressure from the remaining air and the pressure of the water column is created in the neck. Thus, when we remove our hand, the water in the bottle is inclined to pour out. When a small quantity of water pours out, the amount of air in the bottle grows. This decreases the pressure from the water column, and the flow of water stops. Moreover, the force of the water’s surface tension keeps the water contained in the bottle, thus preventing air bubbles from entering the bottle.
The gauze on the neck, in fact, replaces one large hole with several small ones, allowing several small droplets of water to form instead of one larger “drop.” These smaller drops provide more resistance, against both the water pressure from above and the air flow from the atmosphere. When the system reaches equilibrium, the water stops leaking. When sticking a match into one hole in the gauze, we do not “break” the tension of the water in the other holes and therefore the water is still held.