aligned horizontally for all elliptical orbits created in this simulator, where they are
randomly aligned in our solar system.
Animate the simulated planet. You may need to increase the animation rate for
very large orbits or decrease it for small ones.
The planetary presets set the simulated planet’s parameters to those like our solar
system’s planets. Explore these options.
NAAP – Planetary Orbit Simulator 2/8
Tip:
You can change
the value of a slider by
clicking on the slider
bar or by entering a
number in the value
box.

Question 6: (1 point) For what eccentricity is the secondary focus (which is usually
empty) located at the sun? What is the shape of this orbit?
E=0, this is what makes a
circular orbit.
Question 7: (1 point) Create an orbit with a = 20 AU and e = 0.
Drag the planet first to
the far left of the ellipse and then to the far right.
What are the values of r
1
and r
2
at these
locations?

Question 8: (1 point) Create an orbit with a = 20 AU and e = 0.5.
Drag the planet first to
the far left of the ellipse and then to the far right.
What are the values of r
1
and r
2
at these
locations?
r
1
(AU)
r
2
(AU)
Far Left
10
30
Far Right
30
10
(1 point) For the ellipse with a = 20 AU and e = 0.5, can you find a point in the orbit
where r
1
and r
2
are equal?
Sketch the ellipse, the location of this point, and r
1
and r
2
in the
space below. Use document drawing capability or draw by hand to scan and submit.
NAAP – Planetary Orbit Simulator 3/8

Question 9: (1 point) What is the value of the sum of r
1
and r
2
and how does it relate to
the ellipse properties?
Is this true for all ellipses?
r1+r2=2AU+20AU=40AU-2a. This
value is true for all ellipses.
Question 10: (1 point) It is easy to create an ellipse
using a loop of string and two thumbtacks. The
string is first stretched over the thumbtacks which
act as foci.
The string is then pulled tight using the
pencil which can then trace out the ellipse.
Assume that you wish to draw an ellipse
with a semi-major axis of a = 20 cm and e = 0.5.
Using what you have learned earlier in
this lab, what would be the appropriate distances for a) the separation of the thumbtacks
and b) the length of the string?
Please fully explain how you determine these values.
e=c/a and c=ae represent the distance between a focus point and the center of the ellipse.
2c to get the value of the separation of the thumbtacks that is 2c=2ae=2(20cm)
(0.5)=20cm. The length of the string is r
1
+r
2
+2c that is 20cm+20cm+20cm=60cm.