STUDENT INSTRUCTION AND ANSWER
Activity 1: Exploration-The
Motion of the Sun
The four drawings below show
the positions of the Sun and Jupiter at four different times during a
single orbit. Since the Sun and Jupiter account for nearly all the mass
of our solar system we will model our solar system as a two-body problem
involving only the Sun and Jupiter.
A. Does the Sun appear to always
remain in the same position? If not, describe its motion.
B. Estimate the time (in Earth
years) for one orbit of the Sun (this time is known as the orbital period).
How does this time compare to the orbital period of Jupiter?
C. In each diagram, find and label the locations of the center of the
Sun's orbit and the center of Jupiter's orbit. If these two positions
coincide with each other, the position is the Center of Mass (CM) for
D. On each drawing of the Sun
and Jupiter system, sketch a vector to represent the velocity of each
orbiting object. What does the direction of the vector represent? What
does the length of the vector represent? How does the length of the vector
you drew for Jupiter compare to the length of the vector you for
E. When studying motion it is useful to consider the object's velocity
as being made of two components (or parts). The component of velocity
that is directed toward (negative) or away (positive) from the observer's
line of sight is known as the radial velocity. The component of velocity
that is directed perpendicular to the observer's line of sight is known
as the tangential velocity. Imagine that you are the observer shown in
each of the drawings.
i. At which date(s) would
the Sun appear to be moving with a radial velocity?
ii. At which date(s) would the Sun appear to be moving with a tangential
iii. At which date(s) would Jupiter appear to be moving with a radial
iv. At which date(s) would Jupiter appear to be moving with a tangential
F. What would you see in September
1992 from the position of the observer? Draw a sketch like those shown
on the previous page. Include velocity vectors for the Sun and Jupiter.
i. From the location of the observer, does the Sun appear to be moving
with a radial velocity, or with a tangential velocity, or both? Explain
ii. Does Jupiter appear to be moving with a radial velocity, or with
a tangential velocity, or both? Explain your reasoning. Explain your
G. Imagine that you are located at the observer location shown in each
drawing and that there is a satellite located near the Sun on the side
closest to you. If the satellite was sending out a distress signal:
i. At which date would the
message arrive during the shortest interval of time?
ii. At which date would the signal take the greatest amount of time?
iii. During what time interval would the signal have a Doppler shift
to a longer wavelength?
iv. During what time interval would the signal have a Doppler shift
to a shorter wavelength?