Physics 5
Introduction to Astronomy

H. E. Smith                                                                                                       Spring 2007

Quiz 1 Monday 4/9/07

Physics 5 – Spring Quarter 2007

Prof. Smith

Answer Key

 

1) About where is our solar system located within the Milky Way Galaxy?

A. about 10 percent of the way from the center of the galaxy to the outskirts of the galactic disk

B. in the halo of the galaxy above the galactic disk

C. about two-thirds of the way from the center of the galaxy to the outskirts of the galactic disk

D. at the center of the galaxy

E. near the far outskirts of the galactic disk

 

2) Suppose we imagine the Sun to be about the size of a grapefruit. How far away are the nearest stars (the three stars of Alpha Centauri)?

A. the length of a football field

B. 2.5 miles

C. 250 miles

D. 2,500 miles

E. 25,000 miles

 

3) When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?

A. Copernicus misjudged the distances between the planets.

B. Copernicus placed the Sun at the center, but did not realize that the Moon orbits the Earth.

C. Copernicus used perfect circles for the orbits of the planets.

D. Copernicus placed the planets in the wrong order going outward from the Sun.

 

4) Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?

A. The Milky Way is composed of many individual stars.

B. Patterns of shadow and sunlight near the dividing line between the light and dark portions of the Moon's face

C. Phases of Venus

D. Four moons of Jupiter.

 

5) Galileo challenged the idea that objects in the heavens were perfect by _________.

A. inventing the telescope

B. showing that heavy objects fall at the same rate as lighter objects

C. observing sunspots on the Sun and mountains on the Moon

D. proving Kepler's laws were correct

 

7) Suppose a solar system has a star that is four times more massive than our Sun. If that solar system has a planet the same size as Earth, orbiting at a distance of 1AU, what is the orbital period of the planet? Explain.

From Kepler's law, we see that the period depends on the inverse square root of the object masses. Thus, if we have a star four times as massive as the Sun, the period of a planet orbiting at 1AU will be half that of the Earth, or 6 months.