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Density Activity

Answers

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Altitude (meters)
Density (kg/m3)
0
1.22859
100
1.21686
200
1.20521
400
1.18217
800
1.13711
1600
1.05093
3200
0.89362
6400
0.63345
12800
0.27386

  1. Use the data that you recorded to produce a line graph. Use altitude as the independent variable and make a line of best fit. See graph.
    Graph of density versus altitude .. falls to the right
  2. Use your graph to make a general statement on the relationship of density to altitude. As altitude increases, the density decreases with a decreasing rate.
  3. Why do you think this happens? The atoms and molecules in air are held close to the earth by gravity since it has a greater effect close to the surface. The farther away from the surface, the fewer particles there are; so the density is lower.
  4. Convert the following altitudes from meters to feet.
    a) 1000 meters = 3281 feet
    b) 2500 meters = 8202 feet
    c) 6500 meters = 21325 feet
  5. After converting your altitudes to feet, you can calculate (or predict) the temperature at these altitudes by using the following equation: T = 59 - .00356 (h), where h = altitude (in feet). Your temperatures will be in degrees F. Calculate the temperature for each of the altitudes in Question 4.
    a) T1 = 59 - .00356(3281) = 47.3*F
    b) T2 = 59 - .00356(8202) = 29.8*F
    c) T3 = 59 - .00356(21325) = -16.9*F
  6. Use AtmosModeler to check your answers. Be sure the "Units" menu next says "Imperial" to compute in English units. Input each of the altitudes (in feet). Compare your answers for temperature to the AtmosModeler temperatures and explain how any differences may have occurred.
    a) T1 = 47o F
    b) T2 = 29o F
    c) T3 = -17o F
    T1 and T3 appear to be rounded correctly. But T2 is rounded down instead of up.
  7. The temperature may now be used to calculate the pressure of the air at each altitude. Using the equation p = 2116 (T + 459.7 / 518.6)5.256 where T = degrees F and p = lbs/in2, find the pressure that corresponds to each of your temperatures.
    a) T1 = 13.04 lb/sq in (89.86 K - Pascals)
    b) T2 = 10.84 lb/sq in (74.7 K - Pascals)
    c) T3 =6.4 lb/sq in (44.08 K - Pascals)
  8. How does the pressure change compared to a change in altitude?
    The pressure goes down as the altitude increases.
  9. Use a model or table to compare the change in altitude, density, temperature, and pressure at the same time. Include an explanation.
    Altitude (feet)
    Density (slugs/ft3)
    Temperature (oF)
    Pressure (lbs/sq in)

    3281

    .00216

    47

    13.04

    8202

    .00186

    29

    10.84

    21,325

    .00121

    -17

    6.4

    Increase

    Decrease

    Decrease

    Decrease

    As the altitude increases, the density of the air decreases. This, in turn, causes the pressure to drop, as does the temperature.


Related Pages:
Standards
Activity
Worksheet
Lesson Index
Aerodynamics Index

 

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Editor: Tom Benson
NASA Official: Tom Benson
Last Updated: Thu, Jun 12 04:47:14 PM EDT 2014

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