A Barometer is used to measure the atmospheric pressure and is a tool to forecast the weather.
Cut the balloon. Put the balloon on the cup, fix the ruber band so the balloon does not slip off. Glue the bamboo stick (or straw) at the center of the baloon. If the stick is heavy and the can or cup flips over, put some water on it. Use the card board and tape to make it to stand vertically. After the glue is dry, use the cardboard to put some marks and measure the pressure. If the weather is cloudy or raining, put the middle mark above the stick. If the weather is sunny, put the middle mark below it.
After 20 minutes, the “needle” moved. Low pressure is associated with less stable weather patterns, while high pressure is associated with more stable weather patterns. To forecast weather with your barometer, it is important to watch the speed and direction of barometric change. On this case, the needle was going up, that means, the weather will improve.
How it works?
The air inside the cup have a different presure than the outside air, so it makes the balloon to bend outside or inside. If the atmospheric pressure is low, the pressure inside the cup will be higher and it pushes the balloon outside and the stick will point to a lower level.
When the atmospheric pressure is high, the pressure inside will be lower and the stick will point higher.
This is not a “professional” barometer but works fine, excellent for a science project or just for fun.
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