# gravitational lab

Topics: Moon, Gravitation, Solar System Pages: 2 (401 words) Published: December 8, 2013
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Name __________________ Gravitational Lab Go http://phet.colorado.edu/simulations/sims.php?sim=My_Solar_System and click on Run Now.

IAfter the simulation loads click Start.

Describe what you see in this simple sun-planet system.

Specifically, what happens to the central object (the Sun)?
The suns moves also.

Can you explain why the central object moves?
The Sun is pulled by the gravitational forces between itself and the planet
HINT: Is gravitational attraction only the sun pulling on the planet?
Does the planet orbit in a perfect circle? Is the sun at the center?
The planet orbits in an elliptical. No, the Sun is in focus off to the side

II Click Stop and then select 3 bodies. Then Start

Sketch a complete cycle (orbit)
Watch the ‘funny’ object closely
What is it doing? Describe and explain.
The moon orbits the planet that is also orbiting the sun

Could this be the Earth/Moon/Sun system? (Try un-checking Show Traces.)
Yes, but taking a look at the relative masses, this makes a significant difference
Is there anything you are uncomfortable with in the simulation? Explain.
Can you explain the difference in the moon’s path when it is on the right
side of the Sun compared to on the left side? (Turn Traces back on.)
The end points are sharper on the left and the end points are more curved on the right side because the speed of the planet increases when it is closer to the Sun, from Kelper’s 2nd Law

III Click Stop and then select 4 bodies. Then Start

Describe what is happening to the inner planet, why.
The inner planet’s orbit changes because it is disturbed by the outer planet’s gravitational pull.

IV Click Stop and then select 2 bodies again.

Change the mass of the ‘planet’ to 100 units and then Start.
Explain how the motion is different from Part I.
A heavier planet makes the...

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