Astro 1050 Wed. Feb. 2, 2005

Homework #3 questions

Homework solutions (also on board)

Question 1 (1 point)As you're going to sleep early one night you notice the rising moon in the center of the constellation Aries. You get up early the next morning before sunrise to do some flyfishing. The moon is still in the sky, although getting ready to set in the west. What constellation is it in?

a.Aries. b.Cancer. c.Gemini. d.Taurus. e.Pisces.

Why? Because during one night, essentially all the motion of objects in the sky is due to the Earth’s rotation, and everything turns together.

Homework solutions (also on board)

Question 2 (1 point)If a star has a parallax of 0.1 seconds of arc, then its distance is

a.2 parsecs b.5 parsecs c.10 parsecs d. 20 parsecs e.100 parsecs

Question 3 (1 point)In Star Wars, Han Solo claims the Millenium Falcon can make the Kessel Run in less than 12 parsecs. Huh? That's a distance, not a time! Star Wars fans claim this line doesn't refer to a trip in the conventional way, but rather a specific smuggling task through warped space. You should now know where the term parsec comes from. What is the parallax of a star 12 parsecs from Earth?

a. 12 arcseconds. b. 6 arcseconds. c. 1/6 arcseconds.

d. 1/12 arcseconds. e. I don't know what parallax means!

Parallax: Really just the small angle formula

Homework solutions (also on board)

Question 4 Tycho Brahe's greatest contribution to astronomy was

a.his 20 years of careful observations of planetary positions.

b.his model of the universe.

c.his telescopic observations of the moon.

d.his discovery of three laws of motion

Question 5 While all of the following are discoveries of Galileo, which of the four listed is NOT one which DIRECTLY contradicts the "Aristotelian" view of the heavens.

a.The discovery of "imperfections" on celestial bodies, such as mountains and valleys on the moon and changing sunspots on the sun.

b.The discovery of the phases of Venus, ranging from new to crescent to "quarter" to gibbous to full.

c.The discovery that the Milky Way is actually composed of a large number of very faint stars.

d.The discovery of four moons orbiting Jupiter.

Homework solutions (also on board)

Question 6 (1 point)If a space probe were sent into an orbit around the sun that brought it as close as 0.5 AU to the sun and as far away as 5.5 AU, what would be the semimajor axis of its orbit?

a. 0.5 AU b. 3.0 AU c. 5.5 AU d. 6.0 AU

Question 7 (1 point)If a space probe were sent into an orbit around the sun that brought it as close as 0.5 AU to the sun and as far away as 5.5 AU, what would be its orbital period?

a.1.0 years b. 2.5 years c. 4.1 years d. 5.2 years

Work on board using Kepler’s third law: P² = a³.

Homework solutions (also on board)

Question 8 (1 point) An asteroid has an orbital period around the sun of 5.2 years. Using Kepler's third law, how far from the sun is this asteroid?

a.5.2 AU b.10.4 AU c.27.0 AU d.3.0 AU e.2.3 AU

Again on board

Question 9 (1 point) Newton concluded that some force had to act on the moon because

a.the moon moved at a constant velocity.

b.a force is needed to pull the moon outward.

c.a force is needed to pull the moon away from straight-line motion.

d.a force is needed to keep the moon in motion.

e.all of the above.

Homework solutions (also on board)

Question 10 (1 point)What is the circular velocity of Mercury? You will need values from Appendix A of the textbook. You might also find the example in By the Numbers 4-1 on page 62 useful.

a. About 5 km/s.

b. About 25 km/s.

c. About 50 km/s.

d. About 75 km/s.

e.About 100 km/s.

Work on board starting from Vc = (GM/R)^0.5

G = 6.67x10^-11m³/kg s², M=2x10³⁰ kg, R=5.8x10⁷ km


	Question 1 (1 point)As you're going to sleep early one night you notice the rising moon in the center of the constellation Aries. You get up early the next morning before sunrise to do some flyfishing. The moon is still in the sky, although getting ready to set in the west. What constellation is it in? a.Aries. b.Cancer. c.Gemini. d.Taurus. e.Pisces.
	Why? Because during one night, essentially all the motion of objects in the sky is due to the Earth’s rotation, and everything turns together.


	Question 2 (1 point)If a star has a parallax of 0.1 seconds of arc, then its distance is a.2 parsecs b.5 parsecs c.10 parsecs d. 20 parsecs e.100 parsecs
	Question 3 (1 point)In Star Wars, Han Solo claims the Millenium Falcon can make the Kessel Run in less than 12 parsecs. Huh? That's a distance, not a time! Star Wars fans claim this line doesn't refer to a trip in the conventional way, but rather a specific smuggling task through warped space. You should now know where the term parsec comes from. What is the parallax of a star 12 parsecs from Earth? a. 12 arcseconds. b. 6 arcseconds. c. 1/6 arcseconds.
	d. 1/12 arcseconds. e. I don't know what parallax means!


	Question 4 Tycho Brahe's greatest contribution to astronomy was a.his 20 years of careful observations of planetary positions.
	b.his model of the universe.
	c.his telescopic observations of the moon.
	d.his discovery of three laws of motion
	Question 5 While all of the following are discoveries of Galileo, which of the four listed is NOT one which DIRECTLY contradicts the "Aristotelian" view of the heavens. a.The discovery of "imperfections" on celestial bodies, such as mountains and valleys on the moon and changing sunspots on the sun.
	b.The discovery of the phases of Venus, ranging from new to crescent to "quarter" to gibbous to full.
	c.The discovery that the Milky Way is actually composed of a large number of very faint stars.
	d.The discovery of four moons orbiting Jupiter.


	Question 6 (1 point)If a space probe were sent into an orbit around the sun that brought it as close as 0.5 AU to the sun and as far away as 5.5 AU, what would be the semimajor axis of its orbit? a. 0.5 AU b. 3.0 AU c. 5.5 AU d. 6.0 AU
	Question 7 (1 point)If a space probe were sent into an orbit around the sun that brought it as close as 0.5 AU to the sun and as far away as 5.5 AU, what would be its orbital period? a.1.0 years b. 2.5 years c. 4.1 years d. 5.2 years
	Work on board using Kepler’s third law: P² = a³.


	Question 8 (1 point) An asteroid has an orbital period around the sun of 5.2 years. Using Kepler's third law, how far from the sun is this asteroid? a.5.2 AU b.10.4 AU c.27.0 AU d.3.0 AU e.2.3 AU
	Again on board

	Question 9 (1 point) Newton concluded that some force had to act on the moon because
	a.the moon moved at a constant velocity.
	b.a force is needed to pull the moon outward.
	c.a force is needed to pull the moon away from straight-line motion.
	d.a force is needed to keep the moon in motion.
	e.all of the above.


	Question 10 (1 point)What is the circular velocity of Mercury? You will need values from Appendix A of the textbook. You might also find the example in By the Numbers 4-1 on page 62 useful. a. About 5 km/s.
	b. About 25 km/s.
	c. About 50 km/s.
	d. About 75 km/s.
	e.About 100 km/s.

	Work on board starting from Vc = (GM/R)^0.5
	G = 6.67x10^-11m³/kg s², M=2x10³⁰ kg, R=5.8x10⁷ km