# Env Sci/Physics 141: How Planets Work

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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1. Planets are round because of
1. Rotation
2. Gravity
3. Impact
4. Magnetic fields
2. Objects will be round if they are about
1. 10 kilometers or bigger
2. 50 kilometers or bigger
3. A few hundred kilometers or bigger
4. A couple of thousand kilometers or bigger
3. Rotation causes planets to
1. Bulge at the equator
2. Bulge at the poles
3. Wobble irregularly
4. Tilt their axis
4. Temperature affects how well a planet holds an atmosphere because
1. Hot gases rise
2. Temperature determines the velocity of atoms
3. High temperatures break molecules down
4. High temperatures make things evaporate
5. Atoms of gas can escape from a planet
1. If they are hydrogen
2. If they are non-reactive
3. If they exceed escape velocity
4. If they are not bound up in molecules
6. The mass of a planet determines how well a planet can retain an atmosphere because
1. It determines escape velocity
2. It determines what gases the planet has in its atmosphere
3. Large planets lose gases because the atoms are farther away from the center of the planet
4. More massive planets spin slower and are less likely to throw off atoms
7. Even if a planet can otherwise retain an atmosphere, it can still lose it by
1. Centrifugal force
2. Gravitational pull of the Sun
3. Gravitational pull of its satellite
4. Stripping by particles from the Sun
8. The quantity "moment of inertia" is a measure of:
1. How much force it would take to stop a planet in its orbit
2. How fast the planet rotates
3. How mass is distributed within a planet
4. How dense the planet is
5. How many times you hit the snooze alarm
9. A planet with a bulk density of 2.0 gm/cc is most likely
1. All ice
2. Ice with a large rocky center
3. Rock
4. Rock with a metallic core
10. A planet with a bulk density of 4.0 gm/cc is most likely
1. All ice
2. Ice with a large rocky center
3. Rock
4. Rock with a large metallic core
11. A planet with a bulk density of 6.0 gm/cc is most likely
1. All ice
2. Ice with a large rocky center
3. Rock
4. Rock with a large metallic core
12. Bulk density of a planet can be determined from its
1. Diameter and distance from the Sun
2. Diameter and mass
3. Mass and distance from the Sun
4. Diameter alone
5. Mass alone
13. In order to have oceans, lakes or seas, a planet must have
1. The right temperature range
2. The right atmospheric pressure
3. Both a. and b.
4. Neither a. nor b.
14. Tidal forces result from:
1. The rotation of planets
2. The motion of planets around the sun
3. Magnetic interactions between planets
4. The fact that nearby bodies pull more strongly on the near side than the far side
5. Irregular distributions of mass on planets
15. Saturn's density, 0.7 gm/cc, is a strong indication it is mostly made up of:
1. Gas
2. Ice
3. Water
4. Rock

Last Update 25 September 2008; Last Update 14 December 2009

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