Question 1

One au, or 1 astronomical unit, is defined as the

Accepted Answer

A)   distance at which Earth-Sun distance will subtend an angle of 1 arcsecond.
B)   mean distance between the Sun and Earth.
C)   radius of the Sun.
D)   distance traveled by light in 1 year. B

Question 2

A planet's sidereal year is different from its synodic year because the

Accepted Answer

A)   Earth moves.
B)   planet's speed changes along its elliptical orbit.
C)   planet rotates about its own axis in addition to its orbital motion.
D)   the planet moves. A

Question 3

The Copernican system for planetary motions is

Accepted Answer

A)   Earth-centered, with the planets, the Sun, and the stars mounted on crystal spheres, pivoted to allow the correct motions around Earth.
B)   Earth-centered, with the planets moving in epicycles around Earth.
C)   Sun-centered, with the planets moving in elliptical orbits and the Sun at one focus of the ellipse.
D)   Sun-centered, with the planets moving in perfect circles around the Sun. D

Question 4

Venus experiences all of these EXCEPT

Accepted Answer

A)   inferior conjunction.
B)   superior conjunction.
C)   opposition.
D)   greatest elongation.

Question 5

If one uses a force of 100 N to push a packing crate through a distance of 5 m, then the amount of work he has done on the crate is

Accepted Answer

A)   500 kg-m.
B)   20 W.
C)   20 J.
D)   500 J.

Question 6

Kepler's first law states that a planet moves around the Sun in a(n)

Accepted Answer

A)   circle, with the Sun at the center.
B)   elliptical orbit, with the Sun at one focus.
C)   elliptical orbit, with the Sun on the minor axis of the ellipse.
D)   elliptical orbit, with the Sun at the center of the ellipse.

Question 7

A major contribution of Johannes Kepler to the development of modern astronomy was

Accepted Answer

A)   development of the first mathematical heliocentric model of the solar system.
B)   the first model in which planetary orbits are ellipses.
C)   use of parallax to prove that Earth moves around the Sun.
D)   observation of the satellites (moons)  of Jupiter.

Question 8

The Crab Nebula is the result of a supernova explosion of a star that occurred at a distance of about 1.84 kpc from Earth. If people first saw the explosion in A.D. 1054, when did the explosion actually occur?

Accepted Answer

A)   about 1048 A.D.
B)   786 B.C.
C)   1054 A.D., of course
D)   about 4946 B.C.

Question 9

Saturn experiences all of these EXCEPT

Accepted Answer

A)   inferior conjunction.
B)   superior conjunction.
C)   opposition.
D)   greatest elongation.

Question 10

If a tenth planet (tentatively predicted to exist on the basis of perturbations in the orbits of Uranus and Neptune) were to be discovered with a sidereal period of 125 years, what would be the radius of its orbit (assumed to be circular)?

Accepted Answer

A)   8.55 au
B)   125 au
C)   1 au
D)   25 au

Question 11

When Mars is at perihelion it must also be at

Accepted Answer

A)   opposition.
B)   greatest elongation.
C)   superior conjunction.
D)   None of these are correct.

Question 12

An asteroidlike object (or a cometary nucleus) is seen to be orbiting the Sun in a circular path with a period of 120 years. What is its distance of closest approach to Earth (the separation distance when the object is at opposition)? (Be careful with your answer; a diagram might be helpful.)

Accepted Answer

A)   1314.5 au
B)   24.33 au
C)   25.33 au
D)   23.33 au

Question 13

In the heliocentric model of the solar system, which of these phases of Venus should NOT be visible from Earth?

Accepted Answer

A)   full
B)   gibbous
C)   new
D)   None of these are correct; they are all visible.

Question 14

The person who developed the first comprehensive model for a heliocentric cosmology was

Accepted Answer

A)   Kepler.
B)   Ptolemy.
C)   Aristotle.
D)   Copernicus.

Question 15

Kepler's third law, the harmonic law, provides a relationship between a planet's orbital

Accepted Answer

A)   period and the length of the semimajor axis.
B)   eccentricity and the length of the semimajor axis.
C)   period and orbital eccentricity.
D)   period and mass.

Question 16

The greatest inaccuracy in Copernicus's theory of the solar system was

Accepted Answer

A)   no allowance for retrograde motion.
B)   placement of the planets on epicycles, the centers of which followed orbits around the Sun.
C)   the assumption that the planets move in elliptical orbits with constant speeds rather than variable speeds.
D)   placement of the planets in circular orbits.

Question 17

Was Newton's DERIVED version of Kepler's third law the same as the version Kepler discovered by trial and error?

Accepted Answer

A)   Yes.
B)   No. Kepler included the effect of the planet's mass, whereas Newton did not.
C)   No. Newton included the effect of the planet's mass, whereas Kepler did not.
D)   No. Kepler's equation applied only to the inner planets, whereas Newton's applied to all the planets.

Question 18

What did Galileo see when he observed Venus through his telescope?

Accepted Answer

A)   phases like the Moon's
B)   nothing because Venus is perpetually cloud-covered
C)   four satellites (moons)  orbiting Venus
D)   a set of rings

Question 19

An astronomer finds an object at a distance of 5.6 pc from Earth. At this distance, what is the object MOST likely to be?

Accepted Answer

A)   star in our Galaxy
B)   asteroid in our solar system
C)   artificial satellite orbiting Earth
D)   distant galaxy

Question 20

Ptolemy's system of planetary motions, as described in the Almagest, was based on

Accepted Answer

A)   magnetism.
B)   gravitation.
C)   electrical forces.
D)   no underlying physical theory.

Exam 2: Gravitation and the Motion of the Planets