Question 1

The mass of the Sun is about 333,000 times the mass of Earth. Therefore, the gravitational force with which the Sun pulls on Earth is

Accepted Answer

A)  about 333,000 times the gravitational force with which Earth pulls on the Sun. 
B)  about 577 times the gravitational force with which Earth pulls on the Sun. 
C)  the same as the gravitational force with which Earth pulls on the Sun. 
D)  not determined from the masses alone because many other factors are involved.

Question 2

The Sun exerts a gravitational pull on Earth. Why doesn't Earth fall into the Sun?

Accepted Answer

A)  Earth has angular momentum in its orbit around the Sun so Earth is pulled around in a circle. 
B)  Earth also exerts a gravitational pull on the Sun that is equal and opposite to the pull it feels from the Sun. 
C)  Earth and the Sun are kept apart by the interactions of their magnetic fields. 
D)  Retrograde motion counteracts the gravitational pull and keeps Earth from falling into the Sun.

Question 3

Kepler's third law can be described in which of these ways?

Accepted Answer

A)  The time to complete one revolution of its orbit depends on the size or radius of the planet. 
B)  The smaller the radius of a planet, the more rapidly it rotates on its axis. 
C)  The smaller the orbit of a planet, the longer the planet takes to complete one revolution. 
D)  The larger the orbit of a planet, the longer the planet takes to complete one revolution.

Question 4

What actually moves around the Sun along the path usually called Earth's orbit?

Accepted Answer

A)  center of Earth 
B)  point midway between Earth and the Moon 
C)  barycenter of Earth and the Moon 
D)  the center of mass of the Earth-Moon-Sun system

Question 5

When Saturn is at its farthest distance from Earth, it is at

Accepted Answer

A)  inferior conjunction. 
B)  opposition. 
C)  greatest elongation (about 47° from the Sun). 
D)  conjunction.

Question 6

Which of these objects does NOT experience retrograde motion when viewed from Earth?

Accepted Answer

A)  Mars 
B)  Venus 
C)  the Sun 
D)  Pluto

Question 7

According to Newton's second law of motion, an object acted on by a constant net force

Accepted Answer

A)  always moves with a constant velocity. 
B)  always moves with a constant acceleration. 
C)  does not move. 
D)  always moves with a constant speed, although the direction may vary.

Question 8

What use did Tycho Brahe make of parallax in his observations?

Accepted Answer

A)  Tycho did not attempt to measure parallax because he knew it applied only to heliocentric systems-and he believed that the solar system was geocentric. 
B)  Tycho did not attempt to measure parallax because he knew it applied only to geocentric systems-and he believed that the solar system was heliocentric. 
C)  Tycho successfully measured parallax for the supernova of 1572 and the comet of 1577. 
D)  Tycho tried but failed to measure parallax for the stars.

Question 9

In which order (from earliest to latest) did these people make their major contributions to astronomy?

Accepted Answer

A)  Brahe, Copernicus, Newton, Kepler 
B)  Copernicus, Brahe, Kepler, Newton 
C)  Copernicus, Kepler, Brahe, Newton 
D)  Kepler, Copernicus, Brahe, Newton

Question 10

What is the name for a theory that describes the overall structure and evolution of the universe?

Accepted Answer

A)  field theory 
B)  astrology 
C)  cosmology 
D)  astronomy

Question 11

The first major astronomical prediction of Newton's theory of gravitation to be confirmed by observation was the

Accepted Answer

A)  return of Comet Halley. 
B)  supernova of 1572. 
C)  discovery of Pluto. 
D)  discovery of Neptune.

Question 12

Which point in a comet's orbit is closest to the Sun?

Accepted Answer

A)  perihelion 
B)  inferior conjunction 
C)  greatest elongation 
D)  aphelion

Question 13

In which part of the sky could Venus appear at sunset when it is at greatest elongation?

Accepted Answer

A)  due south 
B)  western 
C)  It is not visible because it is on the other side of the Sun. 
D)  eastern

Question 14

The one significant observation Galileo made through his home-built telescope that convinced him that the planets revolved around the Sun was the

Accepted Answer

A)  appearance of the Milky Way as a mass of individual stars. 
B)  discovery of rings around the planet Saturn. 
C)  appearance of mountains and craters on the Moon. 
D)  appearance of Venus following a cycle of phases, from crescent through quarter and gibbous phases to full.

Question 15

How did Copernicus know Mercury was closer to the Sun than Earth?

Accepted Answer

A)  It can always be seen relatively close to the Sun. 
B)  He measured the period and used Kepler's third law. 
C)  He observed it passing through a crescent phase. 
D)  It can be high in the sky at midnight.

Question 16

Viewed from Earth, the largest angular diameter of Venus occurs when it is at what phase?

Accepted Answer

A)  full 
B)  gibbous 
C)  quarter 
D)  new

Question 17

A planet will be observed (through a telescope) to have a crescent shape whenever it is close to which point as seen from Earth? (It may help to draw a diagram and show the sunlit side of the planet on it.)

Accepted Answer

A)  perihelion 
B)  superior conjunction 
C)  opposition 
D)  inferior conjunction

Question 18

The distance to a certain star has been measured to be 750 ly. Expressed in parsecs, the distance is approximately

Accepted Answer

A)  23 pc. 
B)  230 pc. 
C)  750 pc because these units are identical. 
D)  2445 pc.

Question 19

One light-year is the

Accepted Answer

A)  distance that light travels in one year. 
B)  time taken for Earth to orbit the Sun once. 
C)  distance between Earth and the Sun. 
D)  time taken for light to travel from the Sun to Earth.

Question 20

According to the heliocentric theory, which of these objects can never transit (pass in front of) the Sun as seen from Earth?

Accepted Answer

A)  Moon 
B)  Mercury 
C)  Venus 
D)  Mars

Exam 2: Gravitation and the Motion of the Planets