1. What is the name of planet A in the above picture?

A).. B).. C).. D).. E).. |

2. What is the name of planet B in the above picture?

A)... B)... C)... D)... E)... |

3. The planets shown in the figure are sometimes called the outer planets. Why?

A)... B)... C)... D)... E)... |

4. The average density of an object is defined as its

A)... B)... C)... D)... E)... |

You can find a planet or star's average density by dividing its mass M by
4R^{3}/3, where R is its radius. In doing such calculations you need to be SURE to use the proper units. Density is often expressed in grams per cubic cm. Therefore the mass must be in grams and the radius in cm.

For example, suppose we want to calculate the density of Uranus. We therefore
need its mass and radius which we can find in a table of properties of planets. Its mass is 8.68x10^{25} kg. Its radius is 25,559 km. Round this off in the following to 2.6x10^{4} km.

We first convert the mass to grams. One kg = 1000 grams.

Therefore to convert Kgs to gms, simply multiply by 1000 = 10^{3}.

5. What is Uranus's mass in gm?

A)...^{28}.B)... ^{75}. C)... ^{22}. |

We must next convert the radius in km to a radius in cm.

1 km = 1000 meters and 1 meter = 100 cm.

Therefore 1 km = 1000x100 =10^{5} cm.

**Thus, to convert km to cm, multiply by 10 ^{5}. **

6. What is Uranus' radius in cm?

A)...^{-1}.B)... ^{9}. C)... ^{20} |

To now find the density of Uranus. we insert the mass and radius into the formula

= M/(4R^{3}/3)

= 8.68x10^{28}/(4(2.6x10^{9})^{3}/3)

= 8.68x10^{28} /(4x3.14..x(2.6^{3}x10^{9x3}/3)

= 8.68x 10 ^{28-27}/(73.6)

= 1.18 gm/cm^{3}.

You can also find the density of an object by comparing its mass and radius to the mass and radius of an object of known density as follows: a) Increasing the mass by a given factor, increases the density by the same amount.. b) Increasing the radius by a given factor, decreases the density by the amount cubed.

For example: If its mass were the same as the Earth's but its radius were 3
times larger, its density would be 5 gm/cm^{3} /(3^{3}) = 5/27 = 0.185 (approx).
Likewise, if its radius were the same but its mass were 3 times larger, its density would be 5 gm/cm^{3} X 3 = 15 gm/cm^{3}.

7. The Earth's density is about 5 gm/cm ^{3}. If an object's mass were ten times larger and its size the same as the Earth's, its density (in gm/cm^{3}) would be

A)... B)... C)... D)... E)... |

Now combine these results to find the density of Jupiter.

8. Jupiter is 300 times more massive than the Earth and its radius is 10 times larger. What is its density in gm/cm

A)... B)... C)... D)... E)... |

9. Rock has a density of about 3 gm/cm ^{3}, and iron has a density
of about 8 gm/cm ^{3}. What does this suggest about what Jupiter is made of?

A)... B)... C)... D)... |

10. Why do Neptune and Uranus look so blue?

A)... B)... C)... D)... E)... |

11. The planet Neptune is named for what deity?

A)... B)... C)... D)... E)... |

12. The planet Jupiter is named for the Roman King of the Gods. Why is this name appropriate for the planet?

A)... B)... C)... D)... E)... |

13. The planet Pluto is named for what deity?

A)... B)... C)... D)... E)... |

14. What are some reasons that some astronomers feel that Pluto should not be considered an Jovian planet?

A)... B)... C)... D)... E)... |

15. The picture of Jupiter above shows strongly colored bands. These are caused by

A)... B)... C)... D)... E)... |

16. The Coriolis effect plays a role in creating Jupiter's

A)... B)... C)... D)... E)... |

17.The Coriolis effect itself arises because a planet

A)... B)... C)... D)... E)... |

The Coriolis Effect occurs when an object moves across the surface or through
the atmosphere of a spinning planet. Even though the object moves in a
straight line as seen by an observer in space, it moves along a *curved*
path as seen by an observer on the planet. This "twists" air currents that
would otherwise flow from pole to equator into currents that flow around
the planet. Earth's tradewinds and westerlies (such as the jet stream)
arise this way. On the outer planets they create the cloud bands we see
there.

In watching the animation, note that the particle that starts at the pole moves in a straight line (vertically up the screen) but its track on the Earth is curved.

Animation showing how the Coriolis Effect Arises

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