Blaise Pascal's Barometer and Measuring Air Pressure
Materials:
- 1 clean small to medium sized metal can (cookie tins work well)
- 1 large balloon
- 1 needle
- 1 clear plastic drinking straw
- Ruler
- Scissors
- Glue
- Rubber bands (medium to large size, enough to fit around your can)
Instructions:
1. Using your scissors, cut off the end of the balloon (the end that you blow into.)
2. Stretch the balloon over the tin can, making sure that it is taught or tight over the can's opening. Use the rubber bands to seal the can and keep the stretched balloon in place.
3. Glue the needle to one end of the straw. The needle should stick out from the straw by at least an inch.
4. Glue the other end of the straw to the center of the balloon/ can. Your straw will be sticking out to one side of the can.
5. Place your ruler against a wall (glue it on if you're allowed to.) Align your can with the ruler. The pin should be parallel to the ruler so that as it goes up and down, you can take a reading.
This basic barometer has the same elements of Toricelli's and Pascal's. The trapped air inside the can will respond to the outside air pressure. We use a balloon because balloon material is flexible and can expand and retract. When the air pressure is high, the balloon will get pushed down and the straw will go upwards, making the pin go upwards and giving you a high reading. This usually means weather is good. When the air pressure is low, the balloon will get pushed upwards, which means the straw will go downwards, making the pin go downwards and giving you a low reading. This usually means rain is coming.
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