Env Sci/Physics 141: How Planets Work
Steven Dutch, Natural and Applied Sciences,
University
of Wisconsin - Green Bay
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- Planets are round because of
- Rotation
- Gravity
- Impact
- Magnetic fields
- Objects will be round if they are about
- 10 kilometers or bigger
- 50 kilometers or bigger
- A few hundred kilometers or bigger
- A couple of thousand kilometers or bigger
- Rotation causes planets to
- Bulge at the equator
- Bulge at the poles
- Wobble irregularly
- Tilt their axis
- Temperature affects how well a planet holds an atmosphere because
- Hot gases rise
- Temperature determines the velocity of atoms
- High temperatures break molecules down
- High temperatures make things evaporate
- Atoms of gas can escape from a planet
- If they are hydrogen
- If they are non-reactive
- If they exceed escape velocity
- If they are not bound up in molecules
- The mass of a planet determines how well a planet can retain an
atmosphere because
- It determines escape velocity
- It determines what gases the planet has in its atmosphere
- Large planets lose gases because the atoms are farther away from the
center of the planet
- More massive planets spin slower and are less likely to throw off
atoms
- Even if a planet can otherwise retain an atmosphere, it can still lose
it by
- Centrifugal force
- Gravitational pull of the Sun
- Gravitational pull of its satellite
- Stripping by particles from the Sun
- The quantity "moment of inertia" is a measure of:
- How much force it would take to stop a planet in its orbit
- How fast the planet rotates
- How mass is distributed within a planet
- How dense the planet is
- How many times you hit the snooze alarm
- A planet with a bulk density of 2.0 gm/cc is most likely
- All ice
- Ice with a large rocky center
- Rock
- Rock with a metallic core
- A planet with a bulk density of 4.0 gm/cc is most likely
- All ice
- Ice with a large rocky center
- Rock
- Rock with a large metallic core
- A planet with a bulk density of 6.0 gm/cc is most likely
- All ice
- Ice with a large rocky center
- Rock
- Rock with a large metallic core
- Bulk density of a planet can be determined from its
- Diameter and distance from the Sun
- Diameter and mass
- Mass and distance from the Sun
- Diameter alone
- Mass alone
- In order to have oceans, lakes or seas, a planet must have
- The right temperature range
- The right atmospheric pressure
- Both a. and b.
- Neither a. nor b.
- Tidal forces result from:
- The rotation of planets
- The motion of planets around the sun
- Magnetic interactions between planets
- The fact that nearby bodies pull more strongly on the near side than
the far side
- Irregular distributions of mass on planets
- Saturn's density, 0.7 gm/cc, is a strong indication it is mostly made up
of:
- Gas
- Ice
- Water
- Rock
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Last Update 25 September 2008; Last Update
14 December 2009
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