According to the site stats, more than a few students looking for homework answers are being directed by search engines to this blog (probably because this site hosts an online astronomy textbook). WordPress’ site stats show me the exact search terms used, which can be rather amusing. Here is a small sample of the search terms (verbatim) that brought students here:

5. using kepler’s third law of planetary motion, determine the distance in astronomical units the planet jupiter is from the sun, knowing that jupiter takes approximately 11.86 years to orbit the sun one time

Here’s a wild idea: try using Kepler’s third law of planetary motion to determine the distance. The equation is p² = a³, and you’ve been given p. If you don’t know how to determine a, I suggest you ask your middle school math teachers for a refund.

given that the moon has an angular diameter of about 0.5 and an average distance of about 380,000 km from earth, calculate its actual diameter. (hint: recall the angular separation formula)

When I was teaching university classes, it amazed me how often students would overlook the hints I gave them, as though they contained superfluous information (“hint: breathe in and out”). On the contrary, the hints are always meant to be helpful, and often they practically give the answer away, as is the case with the question above. The angular separation formula is basic trigonometry, which you should have mastered in high school; it contains three variables, two of which have been given to you. If this is really beyond your ability to figure out, you should rethink university; it’s only going to get tougher.

how does retrograde motion play a crucial role in defining the differences between the geocentric and heliocentric model?

It’s almost certain you’ve been given this information in a lecture and in the textbook. If you’re going to skip the lectures, at the very least you should scan the book for this information.

knowing that the surface gravity of jupiter is approximately 2.5 that of the earth what would be the approximate weight of a 125 pound person on jupiter

Three variables, two of which have been given. Yes, it’s rocket science (sort of), but the junior version. My 11 year-old homeschooled nephew could do this in his sleep.

the radius of the earth’s orbit around the sun is 1.5 *10^ 11m.if the sun suddenly enlarged

… ?? We’ll never know for sure, but this sounds like a common homework question, which asks how the Earth’s orbit would change if the Sun suddenly enlarged to X size. This is slightly more advanced than the above questions, because it involves thinking about a concept rather than just plugging numbers into a formula or rewording a passage from the textbook. Again, it’s almost certain your textbook covers this concept — time to exercise that grey lump between your ears.

What strikes me as odd about these searches is that the questions are entered word-for-word, which indicates the person searching doesn’t even know what s/he’s being asked. As many years of university-level teaching have shown me, a great many students are not only deficient in the basics (reading, writing, math, and factual information), they aren’t taught how to think, to the point that they cannot parse a very simple problem. These are people who are going to struggle in life.

If you are a student who is too lazy to expend the necessary effort or who struggles with the basics, consider whether you should be spending your time and money on university. It is a serious endeavor that requires your full devotion. If you feel like you’re in over your head, talk to your advisor and be 100% forthright about your struggles. It may be that you should spend a couple of years mastering the basics in community college and/or developing a work ethic before you return to university. There is no shame in acknowledging your deficiencies; on the contrary, it’s a sign of strength.