AP PHYSICS 1
MY SOLAR SYSTEM LAB
Purpose:
Determine the Universal Gravitation Constant “G” for a virtual computer universe.
Procedure:
Use your web browser to navigate to My Solar System Phet at
http://phet.colorado.edu/en/simulation/my-solar-system
Click “Run Now”
By varying the mass of the sun, the mass of the planet, and the velocity of the earth, create a
perfectly circular orbit with the sun at the center of the circle. Use the “tape measure” to verify
that the radius of the orbit is a constant distance from the sun.
Use the timer and the “tape measure” to fill in the data table below.
Create 3 other distinct solar systems (with perfectly circular orbit with the sun at the center of the
circle) by varying either the mass of the sun, mass of the earth, or velocity of the earth.
Data:
Complete the table below with the data from all four solar systems.
Solar System #
1
2
3
4
Radius of Orbit
Period X 10
Mass of Sun
Mass of Earth
Analysis:
Question 1: What net force is causing the centripetal force that makes the earth orbit the sun in
circular motion? __________________
Use the appropriate circular motion equations to fill in the table below
Solar System
#
1
2
3
4
𝑑 = 2𝜋𝑟
𝑡 = 𝑝𝑒𝑟𝑖𝑜𝑑𝑋1
𝑣=
𝑑
𝑡
𝑎𝑐 =
𝑣2
𝑟
𝐹𝑛𝑒𝑡 = 𝑚𝑒𝑎𝑟𝑡ℎ 𝑎𝑐
Isaac Newton answered Question #1 for you. He determined that it was the force of gravity that
caused planets and moons to travel in orbits. His theory led to the Law of Universal Gravitation,
which can be expressed by the equation
|→ | = 𝐺
𝐹𝐺
𝑚1 𝑚2
𝑟2
For our solar system we can rewrite the equation to |→ | = 𝐹𝑛𝑒𝑡 = 𝐺
𝐹𝐺
𝑚𝑠𝑢𝑛 𝑚𝑒𝑎𝑟𝑡ℎ
𝑟2
For each solar system that you created use algebra to calculate “G” which is called the Universal
Gravitation constant and insert it into the table below. For our virtual computer world “G” will
be different than the universe in which we live.
Estimate for “G”
Solar System
1
2
3
4
Average “G” for our lab __________________________________
Conclusion:
Restate the purpose of the lab and whether we fulfilled it. Summarize what we did in the lab
with sufficient detail to replicate. Discuss the relationships we noticed among the variables
including masses, speeds, radii, centripetal acceleration, and force of gravity.
Discuss 3 sources of error.