Name:
NAAP
–
Planetary Orbit Simulator 1/8
Lesson 4 Lab - Planetary Orbit Simulator
Background Material
Answer the following questions after reviewing the “Kepler's Laws and Planetary Motion”
and “Newton and Planetary Motion” background pages.
(1 point) Draw a line connecting each law on the left with a description of it
on the right.
(1 point) When written as P
2
= a
3
Kepler's 3rd Law (with P in years and a in
AU) is applicable to
…
a)
any object orbiting our sun.
b)
any object orbiting any star.
c)
any object orbiting any other object.
(1 point) The ellipse to the right has an eccentricity of
about
…
a)
0.25
b)
0.5
c)
0.75
d)
0.9
(1 point)
For a planet in an elliptical orbit to “sweep out equal areas in equal
amounts of time” it must
…
a)
move slowest when near the sun.
b)
move fastest when near the sun.
c)
move at the same speed at all times.
Kepler’s 1
st
Law
Kepler’
s 2
nd
Law
Kepler’
s 3
rd
Law
Newton
’s 1
st
Law
planets orbit the sun
in elliptical paths
planets with large orbits take a
long time to complete an orbit
planets move faster
when close to the sun
only a force acting on an
object can change its motion
Michael Cruz

NAAP
–
Planetary Orbit Simulator 2/8
d)
have a perfectly circular orbit.
(1 point) If a planet is twice as far from the sun at aphelion than at perihelion,
then the strength of the gravitational force at aphelion will be ____________ as it is at
perihelion.
a)
four times as much
b)
twice as much
c)
the same
d)
one half as much
e)
one quarter as much
Kepler’s 1
st Law
If you have not already done so, launch the NAAP
Planetary Orbit Simulator
.
Open the Kepler’s 1
st
Law tab if it is not already (it’s open
by default).
Enable all 5 check boxes.
The white dot is the “simulated planet”. One can click on
it and drag it around.
Change the size of the orbit with the semimajor axis slider. Note how the
background grid indicates change in scale while the displayed orbit size remains
the same.
Change the eccentricity and note how it affects the shape of the orbit.
Be aware that the ranges of several parameters are limited by practical issues that
occur when creating a simulator rather than any true physical limitations.
We have limited
the semi-major axis to 50 AU since that covers most of the objects in which we are
interested in our solar system and have limited eccentricity to 0.7 since the ellipses would
be hard to fit on the screen for larger values. Note that the semi-major axis is aligned