# Gravitation Lab

Topics: Sun, Orbit, Mars Pages: 3 (863 words) Published: April 9, 2013
Go to http://phet.colorado.edu/simulations/sims.php?sim=My_Solar_System and click on Run Now.

1. Move the slider all the way to accurate, click on the tape measure and the grid. 2. Click the radio button for 4 objects and run the simulation until the purple planet (body 2) has made one complete orbit (one year). 3. After the first orbit (year), turn off the traces (show traces box) and watch another orbit (year) of the purple planet (body 2). Question One:

Is blue moon (body 3) circling the yellow sun (body 1) or the purple planet (body 2)? Explain your answer. Using the trojan asteroids setting it looks like all 3 bodys are orbiting the yellow sun 4. Increase the mass of the sun (body 1) to 400 and allow the simulation to run for one complete orbit of the purple planet (body 2). 5. Decrease the mass of the sun (body 1) to 175 and allow the simulation to run for one complete orbit of the purple planet (body 2). (~90 seconds) Question Two:

How do the orbits of the planets change when the mass of the sun is increased or decreased? Why? Explain your answer. The bigger the sun is the more gravitational pull it it has on the other planets. Therefore when the mass is larger the orbits of each planet are smaller and faster.

Question Three:
Why does the sun (body 1) follow a circular path? How does the path change as its mass changes? Why? Explain your answer. It orbits about a center of mass in the system which doesn’t change. The bigger the mass the smaller the path because there is a greater pull between the sun and the planet. 6. Choose the preset for Sun and Planet from the pull-down menu. 7. Complete the data table below by changing the mass as shown and recording the length of the year in seconds, and also measuring the distance from the planet to the sun at the closest point (perihelion) and farthest point (aphelion). (Make sure slider is set to most accurate) Mass of Sun (body 1)Mass of Planet (body 2)Time of One Orbit (planetary year)...