Introduction to Interactive Physics
Planetary Motion
This program allows us to set up simulations that would be very difficult to set up in the real world. In this simulation, we’re going to look at a planet orbiting a sun (or a moon around a planet if you prefer).
This software allows us to change information and see how it affects the system. These changes can be done with slider bars, or by typing in values in the text box beneath the slider bar (within certain value limits). Write these
values down
before you
change them!!!
5.55 x 109 kg =
= 4.06 x 104 kg
The "ThawSpace"
is where we store files for use in
Physics!!!
Can you
guess
what the
fileS you
need for
this lab is
called?
1) Pre­Lab IP Planetary Motion
2) planet1player
Double click to open the fileS
Make note of the initial masses of both objects: Circle 1 Mass: _______, Circle 2 Mass:______
Press the RUN button and you will see the satellite begin its orbit. 5.55 x 109 kg =
= 4.06 x 104 kg
Law of Universal Gravitation:
Every object in the universe attracts every other object with a force directed along the line of centers for the two objects that is proportional to the product of their masses and inversely proportional to the square of the separation between the objects.
m1m2 F = G
2
d ­11
2
2
G = 6.67x10 N*m /kg
1) Observe the shape of the orbit. Use the slider bar to change the mass of the central object (Circle 1). You need to RESET before changing the values. Try increasing & decreasing the value of central object’s mass. Does the orbit change, and how?
1. Observe AT LEAST one full orbit before
recording observations.
2. You are looking for SIGNIFICANT CHANGES
in the radius/shape of orbit, not at the
change in force on the moon.
3. Read/try question #2 as well before you
record answers for questions 1 & 2.
2) Change the mass of Circle 2 (the satellite) up and down. Again, remember to RESET between changes. Does the orbit change, and how?
Did you read the tips for question 1?
3) Think about earlier discussion of Newton’s Law of Universal Gravitation. Why do you think the answers to #1 & #2 are different? Take your time, think before you answer.
What does Newton's Law of Universal
Gravitation depend on? What do you
change/control in #1 and #2?
m1m2 F = G
2
d 4) Press the RESET button, and then move the sliders to central positions. Press RUN and observe Gravitational Force reading. How does the Gravitational Force relate to the distance between the objects?
1. Read the question before you answer.
2. Observe AT LEAST one full orbit before
you answer this question.
5) Notice only the Force on Circle 2 is represented. What is the Force on Circle 1, and why didn’t I put a ‘display’ for it on the screen?
LIKE
6) RESET once more. Now run the simulation, watching the Velocity of Circle 2. How does the Velocity compare to the distance between the objects. Observe AT LEAST one full orbit before you
answer this question.
7) Decrease the mass of both circles to their minimum values. Run the simulation and allow Circle 2 to move off the screen. Let the simulation continue to run and observe the velocity of Circle 2. Does it increase, decrease, or remain roughly the same? Explain why.
continues to increase as the 1
2
What part of :
satellite continues 2
to move even after it is off the screen?
mm F = G
d v
How does this affect the velocity of the satellite?
8) RESET one last time and change your two masses back to their initial values. At the bottom of the screen you will find a horizontal slider bar. This will allow you to move through various points in the simulation without actually having to run the simulation. Move through one full orbit, and calculate the minimum and maximum distances between our 2 objects. (HINT: F = G*m1m2/d2) Start by solving the equation algebraically for ‘d.’ DO NOT plug in numbers until the end. Show ALL your work. 3 ALGEBRA STEPS MINIMUM!!!
SHOW ALL YOUR CALCULATIONS WITH UNITS IN YOUR CALCULATIONS!!!