Pressure and The Spherical Earth

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Pressure and The Spherical Earth

• Science 10

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Why Does Atmospheric Pressure Exist?

• Because the air in the atmosphere is pulled
  toward the Earth by Gravity
• Currently there is a column of air above you that
  extends approximately 180km up with a mass of
  about 10000kg

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Why Doesnt Atmospheric Pressure Only Push Down
on Us?

• Because a gas is free to move (fills space),
  while it is held to Earth by gravity, it also is
  free to move around objects and we can move
  through it
• Therefore, when we raise our hand, we dont have
  to lift 10000kg of air in order to do so

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Air Pressure Decreases with Altitude
Altitude (km) Pressure (kPa)
0 101.3
1 88.5
2 77.3
3 67.6
4 59.0
5 51.6
7.5 36.8
10 26.2
15 13.3
20 6.8
25 3.5
50 .1

• The further from the surface of the Earth, the
  less air that is above you so the air pressure is
  lower.
• Plot the Altitude versus Pressure data in the
  following table

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Atmospheric Composition

• Nitrogen 78
• Oxygen 21
• Other 1
• Argon
• Carbon dioxide
• Neon
• Helium
• Methane
• Krypton
• Xenon
• Hydrogen
• Ozone

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Latitude

• Degrees north and south of the equator
• Range from 90N (north pole) to 90S (south pole)
  passing through 0 (equator)
• Lines are all equidistance apart

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Longitude

• Degrees east and west of the prime meridian
• Ranges from 180E (international date line) to
  180W (international date line) through 0 (prime
  meridian)
• Lines are furthest apart at the equator and
  closest together at the poles

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Dartmouth High School

• Located at
• 4439N
• 6334W

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Suns Rays

• The angle that the radiation from the Sun strikes
  the Earth is important to local climate
  conditions
• Approximately perpendicular at the equator

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Tilt of the Earth

• Earths poles are not oriented perpendicularly to
  the orbital axis
• This results in seasonal variation
• The angle is approximately 23.5

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Four Seasons

• Four main positions
• Summer solstice (Jun 21)
• Autumnal equinox (Sep 23)
• Winter solstice (Dec 21)
• Vernal equinox (Mar 20)

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Circles and Zones

• Arctic Circle
• 24 hours of daylight during NH summer
• Antarctic Circle
• 24 hours of daylight during SH summer
• Tropic of Cancer
• Direct sunlight on Jun 21
• Tropic of Capricorn
• Direct sunlight on Dec 21