Physics 101 DIY : Make and Use a Barometer to Measure Air Pressure Overview Air pressure is the result of the weight of tiny particles of air (air molecules) pushing down on an area. While invisible to the naked eye (i.e. microscopic), they nevertheless take up space and have weight. For example, take a deep breath while holding your hand on your ribs and observe what happens. Did you feel your chest expand? Why did it expand? Air pressure expands because the air molecules take up space in your lungs, causing your chest to expand. Furthermore, air can be compressed to fit in a smaller volume since there's a lot of empty space between the air molecules. When compressed, air is placed under high pressure. Meteorologists measure these changes in the air to forecast weather, and the tool they use is a barometer. The common units of measurement that barometers use are millibars (mb) or inches of mercury. DIY Make a Barometer A. Materials o B. Theory How does this measure air pressure? C. Procedure 1. Place the completed barometer and scale in a shaded location free from temperature changes (i.e. not near a window as sunlight will adversely affect the barometer's results). 2. In your notebook or the table below, record the current date, time, the weather conditions, and air pressure (i.e. the level where the end of the straw measures on the scale). 3. Continue checking the barometer twice a day (if possible) each day over a four days period. Date Data Table Weather Air Time Conditions Pressure Date June 4, 2003 June 4, 2003 June 5, 2003 Sample Data Table Weather Air Time Conditions Pressure Clear and 9:30 am 4 Sunny 2:30 pm Cloudy 3 9:30 am Rainy 1 Barometer Analysis Answer the following questions in complete sentences. 1. What problem were you trying to solve with your barometer? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 2. Were there any changes in the weather during the week? ___________________________________________________________________________ ___________________________________________________________________________ 3. Did the barometer measurement change when the weather changed? How much? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 4. Did the barometer measurement change without a change in weather? Why do you think that happened? ___________________________________________________________________________ ___________________________________________________________________________ 5. How well did your barometer work? ___________________________________________________________________________ ___________________________________________________________________________ 6. What would you change if you could design the barometer again? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 7. How do the barometer measurements help us understand the system of weather around us? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Chapter Five (3517352) Celsius? 0/1 points 0/35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 0/1 0/1 0/1 0/1 0/1 0/1 0/2 0/1 0/2 0/1 0/1 0/1 0/1 0/1 0/2 0/1 0/2 0/2 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/4 pressure? 0/1 points °C m °C be 9 cm (0.09 m) shorter? 0/1 points J J 2°C. How much heat is transferred from the water to cool it to 2°C? 0/1 points Total 0/35 OBInPhys7 5.P.002. [2182673] OBInPhys7 5.P.010. [2182676] OBInPhys7 5.P.014. [2182650] A bottle containing 4 kg of water at a temperature of 15°C is placed in a refrigerator where the temperature is kept at 0/1 points Air in a balloon does 39 J of work while absorbing 83 J of heat. What is its change in internal energy? OBInPhys7 5.P.008. [2182667] An aluminum wing on a passenger jet is 36 m long when its temperature is 29°C. At what temperature would the wing OBInPhys7 5.P.006. [2182696] A lead vat is 19 m long at room temperature (20°C). How much longer is it when it contains boiling water at 1 atm OBInPhys7 5.P.004. [2182672] On a nice winter day at the South Pole, the temperature rises to −45°F. What is the approximate temperature in degrees 0/1 points Points Question Current Score: 1. 2. 3. 4. 5. 6. A 0.07­kg lead bullet traveling 267 m/s strikes an armor plate and comes to a stop. If all of the bullet's energy is °C converted to heat that it alone absorbs, what is its temperature change? ­ ­ ­ ­ ­ ­ 7. 8. 9. 10. 11. 0/2 points °C the dew point?) OBInPhys7 5.P.018. [2182669] OBInPhys7 5.Q.001. [1981831] (b) To what temperature could the air be cooled before condensation would start to take place? (That is, what is kg/m3 (a) What is the humidity? On a summer day in Houston, the temperature is 30°C and the relative humidity is 42 percent. 0/1 points OBInPhys7 5.Q.002. [1981669] What are the three common temperature scales? What are the normal boiling and freezing points of water in each scale? 0/2 points OBInPhys7 5.Q.004. [1981664] OBInPhys7 5.Q.003. [1981910] The Fahrenheit and Celsius temperature scales agree at ­40° (­40°C = ­40°F). Do the Fahrenheit and Kelvin temperature scales ever agree? Yes No How about the Celsius and Kelvin scales? 0/1 points What is the significance of absolute zero? 0/1 points What happens to the atoms and molecules in a substance as its temperature increases? ­ ­ ­ ­ ­ 12. 13. 14. 15. 0/1 points OBInPhys7 5.Q.006. [2182655] Air molecules in a warm room (27°C = 300 K) typically have speeds of about 500 m/s (1,100 mph). Why is it that we are unaware of these fast­moving particles continuously colliding with our bodies? the collision with a human body. The mass of an air molecule is so miniscule that its momentum and kinetic energy are too small to be evident in The effect of these collisions tend to cancel out. Because the air molecules are everywhere around us they constantly collide with our bodies from all directions. transferred to our bodies when the collisions with a human body occur. OBInPhys7 5.Q.011. [2182648] OBInPhys7 5.Q.008. [1981551] The size of an air molecule is extremely small, so its momentum and kinetic energy are not efficiently The density of the warm air is so low that the air molecules tend to miss our bodies. 0/1 points Explain what a bimetallic strip is and how it functions. 0/1 points What is unusual about the behavior of water below the temperature of 4°C? specific heat of most substances is halved. Within the range of 0°C to 4°C the specific heat of water doubles when the temperature decreases, whereas the contract. Within the range of 0°C to 4°C water expands when the temperature decreases, whereas most substances expand. Within the range of 0°C to 4°C water contracts when the temperature decreases, whereas most substances the specific heat of most substances is doubled. OBInPhys7 5.Q.012. [1981768] Within the range of 0°C to 4°C the specific heat of water is halved when the temperature decreases, whereas 0/2 points A company decides to make a novelty glass thermometer that uses water instead of mercury or alcohol. (a) The thermometer would include a warning informing the user that it should not be exposed to temperatures below 0°C. Why? (b) Suppose the thermometer is taken outside where the temperature is 1°C. Describe how the level of the water would change as it adjusts to the new temperature and how at some point it would behave very differently than a mercury­ or alcohol­filled thermometer. ­ ­ ­ ­ 16. 17. 18. 19. 0/1 points OBInPhys7 5.Q.013. [1981563] OBInPhys7 5.Q.014. [1981676] What are the two general ways to increase the internal energy of a substance? Describe an example of each. 0/2 points OBInPhys7 5.Q.016. [1981453] OBInPhys7 5.Q.015. [1981593] Air is allowed to escape from an inflated tire. Is the temperature of the escaping air higher than, lower than, or equal to the equal lower higher temperature of the air inside the tire? Why? 0/2 points Is it possible to compress air without causing its internal energy to increase? Yes No If so, how? 0/1 points Describe the three methods of heat transfer. Which of these are occurring around you at this moment? ­ ­ ­ ­ 20. 21. 22. 23. 24. 25. 0/1 points A potato will cook faster in a conventional oven if a large nail is inserted into it. Why? 0/1 points A coin and a piece of glass are both heated to 60°C. Which will feel warmer when you touch it? piece of glass coin 0/1 points OBInPhys7 5.Q.017. [1981479] OBInPhys7 5.Q.018. [1981465] OBInPhys7 5.Q.019. [1981805] OBInPhys7 5.Q.022. [1981472] OBInPhys7 5.Q.020. [1981449] A submerged heater is used in an aquarium to keep the water above room temperature. Should it be placed near the surface of the water or near the bottom to be most effective? near bottom near surface 0/1 points On a cool night with no wind, people facing a campfire feel a breeze on their backs. Why? 0/1 points OBInPhys7 5.Q.024. [2191265] When heating water on a stove, a full pan of water takes longer to reach the boiling point than a pan that is half full. Why? 0/1 points In this example, is it really necessary to know the mass of the concrete block to solve this problem? Put another way, would the answer be different if it was a 10­kg block that was dropped instead of a 5­kg one? Yes No ­ ­ ­ ­ ­ ­ 26. 27. 0/4 points water to put out fires, but if the ‑‑‑Select‑‑‑ OBInPhys7 5.Q.026. [2182660] were the same, the heat The specific heat capacity of water is extremely high. If it were much lower, say, one­fifth as large, what effect would this second. need ‑‑‑Select‑‑‑ cooling systems so that a ‑‑‑Select‑‑‑ Last Saved: Jan 24, 2016 09:55 PM EST Author: Murdock, Maajida ( Maajida.Murdock@MORGAN.EDU ) Locked: Yes Code: Category: Homework Submissions Allowed: 5 Name (AID): Chapter Five (3517352) Help/Hints Add Practice Button Mark Question Part Score Publish Essay Scores Assignment Score Question Score Before due date Feedback Settings OBInPhys7 5.Q.027. [1981767] of water would flow through the engine each taken from the fire as the water boils would still be responsible for most of the cooling. Water cooled engines would It would take ‑‑‑Select‑‑‑ have on processes like fire fighting and cooling automobile engines? 0/1 points Why does the temperature of water not change while it is boiling? 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