Gravity Internet Lab 5 points October 2005 PHY 151/161 Name ____________________________

Login to Blackboard. These URL’s are available in the Web Sites section of our Blackboard page. OR you can manually enter the URL. Do the activities outlined below. Give each activity a rating of 1 – 10. 10 represents an extremely worthwhile activity. 1 represents an almost worthless activity. Write all of your answers on the back of this page.

_____ 1. http://www.humnet.ucla.edu/humnet/french/faculty/gans/java/SolarApplet.html

Read the instructions. Click the – button a few times such that the entire orbit is in one window. Unfortunately this does not reduce the size of the sun. The path of Mercury’s orbit does not actually pass through the sun! Click the ON button. Observe. Why do the inner planets have shorter periods? To answer this question, combine the gravitational force equation and the centripetal force equations. Replace V with 2*pi*r/t . Solve for t.

Show your work on the back of this page.

_____ 2. http://www.phy.ntnu.edu.tw/java/Others/impact/impact.html

Read some of the instructions. Click the start button. Try changing mgravity and vgravity and observe. Click the mouse near one of the objects to pull it to the mouse position. Drag it and release the mouse button. Click the trace on if you wish. Explain (on the back of this page) why the smaller (less mass) object has more variation in its path of motion than the large mass object.

____ 3. Your Weight on Other Worlds http://www.exploratorium.edu/ronh/weight/index.html

Enter 140 (pounds) in the text box. Click on Calculate. Scroll down. What is this person’s weight on Jupiter?

Optional: Enter your weight. Don’t write down the results for your weight.

____ 4. Gravitation 3.8 http://www.arachnoid.com/gravitation/index.html

Scroll down. Click on the drop down arrow to the right of the text box. Select Planetary System + Comet if it is not already selected. Click on GO. Observe. TRUE or FALSE The inner planets should move faster than the outer planets. Select Chaotic Planetary System. Click on GO. Observe.

_____ 5. Many Orbit Demonstrations http://burtleburtle.net/bob/physics/orbit101.html

Click on a picture to start the simulation. Click again to stop the motion. There are no questions for this site.

optional _____ 6. Kepler’s Third Law http://jersey.uoregon.edu/vlab/kepler/Kepler.html

If you have an interest in Astronomy you should visit this site. You can find the approximate time between close approaches of Mars to the earth by using the start and stop buttons. You can drag Mars to a different size orbit and observe the change in the period.

Due Next Week Find a magazine or Internet article which discusses one of the following topics: Kepler’s Laws, Newton’s Development of the Law of Gravitation, a practical use today of measurements of ‘g’, artificial gravity in a spacecraft which is orbiting the earth, an experiment which shows that gravitational mass and inertial mass are equivalent, spacecraft that have left the solar system, or the "three-body" problem. Read the article. Write neatly or type a one-page summary of the article and turn in the summary with this page next week. Write your name, the name of the magazine, month, year, page number and title of the article, or URL, at the top of your summary page. Everyone should summarize a different article.

BONUS 1 point Find the URL of a site not on this page (or in Blackboard) that has a good JAVA simulation of gravity. No two URL’s or magazine references submitted by different students can be the same.