Lab assignement 1

Exercise 4-2: Atmospheric Pressure and Hurricanes

Exercise Inventory

( Note: You must provide the materials listed in *red. work well.) *Paper towels ger than the ping pong ball. Aquafina® bottles *Tap water wide openings will not work, as they can’t be big- (1) Underpad (glass works best but plastic is ok. Bottles with Ruler *(1) 20 oz. Soda/Water bottle (1) Ping pong ball *Internet access (1) 100 mL Graduated cylinder *Calculator Materials (1) 250 mL Beaker )

EXERCISE 2: ATMOSPHERIC PRESSURE AND HURRICANES

In this laboratory exercise, you will use common items to make your own homemade barometer to measure the current atmospheric pressure in your home. Then you will use real data from Hurricane Matthew to analyze the connection between atmospheric pressure and storm strength.

PROCEDURE

Part 1: Measuring Atmospheric Pressure

1. Obtain a 20 oz. glass or plastic bottle and empty its contents. Rinse out the bottle several times with tap water and remove any labels on the outside of the bottle.

2. Fill the bottle all the way to the top with tap water.

3. Carefully pour 90 mL of water from the bottle into the graduated cylinder. Record this volume in the V0 row of Table 4 on the Exercise 2 Data Sheet. Leave the 90 mL of water in the graduated cylinder.

Note: Remember to read the level of water in the graduated cylinder from the bottom of the meniscus. If you need a

demonstration of how to do this, watch the How to Read the Meniscus instructional video.

4. Bring the 250 mL beaker and the ruler in front of you so they are within reach.

5. Hold the ping pong ball on top of the mouth of the bottle and invert it over the beaker. Hold the ball securely over the mouth of the bottle. Small drops of water should drip over the ball and into the beaker, but no air should get into the bottle.

Note: Do not jiggle the ball in any way while you are doing this. You can very slowly rotate the ball around the mouth of the bottle just a little, but it must maintain contact with the bottle while you do this. Only a little bit of water

(a couple mL) should dribble out around the ball, and no air bubbles should make their way into the bottle.

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6. If any air gets into the bottle, flip the bottle back over, remove the ping pong ball, and pour the water that’s in the beaker back into the bottle and start at Step 5 again.

7. After holding the bottle inverted for a minute or so, enough water will leak out so that the pressure on both sides of the ball is the same. You can take your hand away from the ball and it will stay in place (Figure 9).

Figure 9. When the pressure has equilibrated, the ball will remain stuck to the opening of the inverted bottle, like the one shown here.

8. If the ball falls out into the beaker and the water starts to spill out, try to contain all the water inside the beaker. Then quickly hold the bottle upright again, so you lose as little water into the beaker as possible. Pour the water in the beaker back into the bottle and start at Step 5 again.

9. Once you have gotten the ball to stay attached to the mouth of the inverted bottle, use your free hand to measure the distance (in cm) from the mouth of the bottle to the top of the water in the inverted bottle (Figure 10) with the ruler. Round to the nearest millimeter. Record this value in the D (cm) row in Table 4 on the Data Sheet.

Figure 10. Location of where to measure along the bottle to obtain (D). P0 = the atmospheric pressure in the room, V0 = the initial volume of water poured from the bottle, P1 = the pressure in the bottle after removing some water, V1 = the total amount of water removed from the bottle.

10. Hold the ping pong ball in place again and flip the bottle back over and set it down on the table.

11. Convert the distance you measured (D) from cm to m and record it in the D (m) row in Table 4.

Note: If you need a refresher on how to do metric conversions, watch this Key Technique video about how to con- vert between units.

12. Pour all the water that leaked into the beaker into the graduated cylinder that still contains the 90 mL of water. Measure the total volume of the water and record it in Table 4 in the V1 row.

Note: Remember to read the level of water in the graduated cylinder from the bottom of the meniscus.

13. Use the equation below and the values in Table 4 to solve for the atmospheric pressure in the room, P0:

Equation (1)

where ρ (Greek letter rho; pronounced “row”) is the density of water (approximate), g is the acceleration of gravity, D is the distance from the top of the water to the mouth of the bottle (in meters), V0 is the initial volume of water poured from the bottle, and V1 is the total amount of water removed from the bottle.

14. Show your work in the space below Table 4 and record your result for P0 in Table 4. Your result for atmospheric pressure will be in Pa (Pascal).

15. Go to the National Weather Service website and type in your zip code or city in the search bar (top left corner of the page) to find the current weather conditions in your area. Record the barometer reading in millibars (mb) in the space provided below Table 4.

16. Convert the pressure in mb to Pa using the conversion factor 1 mb = 100 Pa. Record this value in the space provided below Table 4.

Part 2: Analysis of Hurricane Matthew

1. A selection of data from the National Hurricane Center recorded from Hurricane Matthew is shown in Table 5 on the Exercise 2 Data Sheet. You will use this data to complete Part 2 of this exercise.

2. Convert the maximum wind speed from knots to miles per hour (mph) and record your results in the “Max Wind Speed (mph)” column in Table 5. Use the conversion factor 1 knot = 1.15 mph.

3. Use the Saffir-Simpson Wind Scale (in Table 2 of the Introduction) to give the storm a category rating for each data point. Record your answers in the “Category” column in Table 5.

4. Construct a graph of the Max Pressure (mb) vs. Max Wind Speed (mph). Place the max pressure on the x-axis and the wind speed on the y-axis. You can use a graphing program to create your graph or draw one by hand. Include your graph with the completed Exercise 2 Data Sheet.

Note: Remember to include a title, label your axes, and include units.

5. Answer the Post-Lab questions.

Table 4. Atmospheric Pressure Calculations

Variable	Value
V0 (mL)	90ml
D (cm)	16.6 cm
D (m)	0.166 m
V1 (mL)	123 mL
ρ (kg/m3)	1000
g (m/s2)	9.8
P0 (Pa)

Solve for P0 and show your work below:

Equation (1)

Current barometer reading from the NWS website (mb): Current barometer reading converted to Pa:

( E xercise 2 Dat a Sheet )

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Table 5. Hurricane Matthew Data

Date	Max Pressure (mb)	Max Wind Speed (knots)	Max Wind Speed (mph)	Category
09/28/2016	1009	50
09/29/2016	993	65
09/30/2016	968	100
10/01/2016	942	140
10/02/2016	947	130
10/03/2016	942	125
10/04/2016	935	130
10/05/2016	960	110
10/06/2016	937	120
10/07/2016	937	115
10/07/2016	946	100
10/08/2016	957	85
10/08/2016	973	70
10/09/2016	981	70
10/09/2016	987	60
10/10/2016	990	55