Air Pressure Activities Answers
The following are examples of answers to the questions that accompany these activities.
1. Gravitational for is pulling down.
2. The water in the straw does not move.
3. A vacuum is created in that space (although water vapor and air dissolved in the water reduces that vacuum).
4. Because air pressure that was able to push down on the column of water balanced the air pressure that was pushing up on the column of water. With those two forces balanced, the gravitational force is an unbalanced force pulling down on the column of water.
5. The height of the water in the tube typically will range from 385 inches of water on a cloudy stormy day to 415 inches of water on a day when there are very few clouds.
6. The barometer is very tall and the water would freeze if the barometer were outside during very cold weather. Some water can also evaporate into the space above the water column inside of the tube.
7. The barometric pressure will typically range from 28 inches of mercury to 31 inches of mercury.
8. Fill a tube with mercury. Seal the top end of the tube. Hold the tube in a vertical position with the opened bottom of the tube in a pool of mercury.
9. The downward pull of gravity is balanced by the air pressure exerted against the surface of the pool of mercury
10. Because air pressure would be able to push down on the column of mercury to balance the air pressure that was pushing up on the column of mercury. With those two forces balanced, the gravitational force is an unbalanced force pulling down on the column of mercury.
11. Set up a proportion. If students are not informed that mercury is 13.6 times more dense than water they determine that value using the data table on page 3.
10,336 mm of water/ 760 mm of Hg = 13.6.
12. There is typically a 10 to 15 percent difference between the experimental value for barometric pressure and the value obtained from a weather report.
13. The clamp at the top of the tube may not have formed a tight seal. Water evaporated into the space above the column of water. Air dissolved in water entered the space above the column of water. The tube was jostled as it was lowered and some water escaped from the bottom of the tube.
14. A proportion can be used to determine the pressure in a variety of pressure units.
Air Pressure Answers Page 2
Design a Demonstration: Select a thickness of paper or layers of paper so that a square meter of the paper has a mass of 100 grams. A smaller demonstration would be to reduce the area and mass proportionately.
15. The fluid in a mercury barometer is a liquid. The fluid in an aneroid barometer is a small amount of air.
16. a. The volume will decrease.
16. b. The volume will increase.
17. The rod that is touching the flexible container is also attached to a level mechanism that move a needle pointing the a scale.
18. a. Some air leaves you middle ear until the air pressures are equalized.
18. b. Some air enters you middle ear until the air pressures are equalized.
19. The air pressure inside would increase and cause the can to burst.
20. The number of air molecules is decreasing. The remaining molecules have a greater kinetic energy and are able to keep the pressure inside of the can the same as the air pressure outside of the can.
21. The can collapsed. (This does not always work the first time for some mysterious reason.)
22. The can stopped collapsing.
23. No fluid is moving from one flask to another.
24. Air bubbles are moving through the fluid in Flask A.
25. When the water in Flask B is boiling rapidly the bubble reaching Flask A contain a lot of water vapor and condense into liquid in the water in Flask A.
26. Fluid in Flask A is pushed into Flask B.