Homeworks 1
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Homeworks 1 is the attempted solution to our second task[1] in the course Introduction to Astrophysics. This assignment is due on Wednesday 09/09/09 and was assigned on 09/01/09. Solutions were created by Group 1 (RyanT, KimW, SaraC, ZackM, TiaraD) to be completed by 09/11/09.
Problem 1
List in order of increasing size and give the approximate size of the following objects: An atom, a biological cell, a cluster of galaxies, the Earth, a galaxy, the Local Group of galaxies, a neutron, a neutron star, a person, the Solar System, our sun. Note: you may have to look in other books besides your textbook to get all this information.
There are 3 ways to approach this problem: By radius, by volume, and by mass. This problem coincides with Lecture #2
By Radius
- Neutron = (or = ) [2] [3] [4]
- Atom = empirical atomic radius = [5] [6]
- Biological Cell = = [7] [8]
- Person = height = 4'11" = [9]
- Neutron Star = = [10] [11]
- Earth = radius of the Earth = = [12]
- Sun = radius of the Sun = = [13]
- Solar System = radius of the comet Oort Cloud's orbit = = [14]
- Galaxy = radius of most galaxies = = [15]
- Local Group of Galaxies = radius of Local Group = = [16]
- Cluster of Galaxies = approximate size of most clusters = = [17]
By Volume
To be Completed
By Mass
To be Completed
Problem 2
The nearest star outside the solar system is about 4 light years away.
- How far away is the star in kilometers?
- Suppose you travel to the nearest star in a rocket ship moving at 100 km per hour (100 km/hr is
about 62 mi/hr, a typical automobile speed on a Florida highway). How many years will it take you to get to the star?
- Suppose you travel to the star at 10 km per second (the speed of a rocket in orbit around the Earth). How many years will it take you to get to the star?
Problem 3
Use the size of the Astronomical Unit in kilometers and the length of the year in seconds to calculate how fast the Earth moves in its orbit in kilometers/second.
Problem 4
Describe the essential differences between the Ptolemaic, Copernican, and Keplerian descriptions of planetary motion.
Problem 5
Use Newton’s laws to show that the orbits of planets are ellipses.
Kepler's First Law is that the orbits of our planets are ellipses (with the sun at one focal point). However it does not explain why the planets move as they do in elliptical loops. Therefore, this question can be restated: Use Newton's laws to derive Kepler's First Law.
The Equation for an Ellipse is:
Notes
- ↑ Our first task was to register our PRS, visit the course web-page on Blackboard, look at the textbook, and write an equation for our wiki
- ↑ Which is larger, the proton or the neutron? http://www.physlink.com/education/AskExperts/ae570.cfm
- ↑ What are the sizes of protons neutrons and electrons? http://wiki.answers.com/Q/What_are_the_sizes_of_protons_neutrons_and_electrons
- ↑ On the Radius of the Neutron, Proton, Electron and the Atomic Nucleus http://www.wbabin.net/physics/yue.pdf
- ↑ Information about Atomic Radii: http://www.webelements.com/
- ↑ J.C. Slater, J. Chem. Phys. 1964, 41, 3199.
- ↑ The Biological Cell on Wikipedia http://en.wikipedia.org/wiki/Cell_(biology)
- ↑ Campbell, Neil A.; Brad Williamson; Robin J. Heyden (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 0-13-250882-6
- ↑ Kim Wynne's height
- ↑ http://en.wikipedia.org/wiki/Neutron_star
- ↑ Paweł Haensel, A Y Potekhin, D G Yakovlev (2007). Neutron Stars. Springer. ISBN 0387335439.
- ↑ Google "radius of the Earth"
- ↑ Google "radius of the Sun"
- ↑ http://curious.astro.cornell.edu/question.php?number=374
- ↑ http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/001205a.html
- ↑ http://www.universetoday.com/guide-to-space/galaxies/local-group/
- ↑ http://www.damtp.cam.ac.uk/user/gr/public/gal_lss.html
References
- B.W. Carroll & D. A. Ostlie (2007). An Introduction to Modern Astrophysics (Chapter 2). Addison Wesley. ISBN 0-8053-0402-9
- Lecture #2
- Lecture #3
- Lecture #4