Open gravity force lab (http://phet.colorado.edu/simulations/sims.php?sim=Gravity_Force_Lab )
Part I: Force of Gravity
- What is true about the force of m2 on m1, and the force of m1 on m2 (two things) __________________________________________________________________2. Set both masses equal to 25 kg, and set them both 4 m apart. You can move the masses and rulers.
- What is the force of gravity? ___________________ Compare the following answers to this answer.
- Keep the masses 4 m apart, but change one mass to 50 kg.
- What is the new force of gravity? _____________________
- How did it change (compared to #4)? ___________________________________
- Change the 50 kg mass down to 12.5 kg.
- What is the new force of gravity? _____________________
- How did it change (compared to #4)? ___________________________________
- Set both masses back to 25 kg, but move them so they are 8 m apart.
- What is the new force of gravity? _____________________
- How did it change (compared to #4)? ___________________________________
- Given the two masses of 25 kg 8 m apart, how can you change one mass to get back to the answer in #4? _____________________________________________
Open my solar system (http://phet.colorado.edu/simulations/sims.php?sim=My_Solar_System)
Part II: Planetary Motion
I After the simulation loads click Start.
Sketch and describe (your paper) what you see in this simple sun-planet system.
Specifically, what happens to the central object (the Sun)?
Can you explain why the central object moves?
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?
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.
Could this be the Earth/Moon/Sun system? (Try unchecking Show Traces.)
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.)
III Click Stop and then select 4 bodies. Then Start
Describe what is happening to the inner planet, why.
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.
Ever hear of a binary star?
Repeat with both bodies at 200 units of mass.
V Click Stop and then select 3 bodies again.
Change the masses of bodies 2 and 3 to 5 units each and Start.
Watch for several orbits and explain what’s happening.
Open lunar lander (http://phet.colorado.edu/simulations/sims.php?sim=Lunar_Lander)
Part III: Lunar Lander
- Play the game. Your goal is to have the maximum number of landings before you run out of fuel. Try to keep the landings soft and avoid the boulders.
- How many landings did you achieve? ___________________________________
- What was difficult about this game? ____________________________________ __________________________________________________________________