A barometer is a tool used to measure air pressure. Air pressure is one of the many factors that influence our weather. It is measured in pounds per square inch. The force of air pressure exists in all different directions. That is why we do not feel it.
With our homemade barometer, we can measure relative air pressure. We can determine if the air pressure is high or low, but not an exact pressure in pounds per square inch. Our readings can help us predict the weather.
High air pressure is a sign of nice weather. The force of the air is strong enough to push the clouds up and away. On our barometer, high air pressure will push down on the balloon, causing the pointer to raise.
Low air pressure can mean rain. When the air pressure is low, there is not enough force to push the clouds away, and we get precipitation. In this case, the force of the air trapped in the can is stronger and pushes up on the balloon. This causes the pointer to lower.
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