AY 101-002                      QUIZ #2                            Spring 2008

Answer each of the following on a computer-gradeable answer sheet. Be
sure to fill in your name and student number (and blacken their circles as 
well). 

1. Among Galileo's discoveries, the one most directly distinguishing between
   Copernicus' Sun-centered scheme and the old Earth-centered one was
   a) moon of Jupiter.                     c) sunspots.
   B) THE PHASES OF VENUS.                 d) lunar craters and mountains.

2. Building on the measurements by Tycho, Kepler found that planetary orbits are
   a) circles.
   b) ellipses centered on the Sun.
   C) ELLIPSES WITH THE SUN AT ONE FOCUS.
   d) hyperbolic curves.

3. Newton found that the gravitational force between two objects
   a) depends only on their masses. 
   B) DEPENDS ON THEIR MASSES AND SEPARATION.
   c) depends on their chemical composition.
   d) changes with time.

4. As shown in Kepler's second law, an object in an elongated orbit
   a) maintains a constant speed throughout.
   B) MOVES FASTEST WHEN NEAREST THE sUN.
   c) moves fastest when farthest from the Sun.
   d) requires a constant supply of energy to maintain this path.

5. The Earth has 80 times the mass of the Moon. If we set the gravitational
   force with which the Earth pulls the Moon equal to 1, the force with
   which the Moon pulls the Earth is
   a) 80                                  c) 1/80
   B) 1                                   d) zero.

6. One strong point in favor of Copernicus' view of the solar system, even
   before there was definitive evidence, was
   a) its more accurate predictions of planetary positions.
   B) ITS DRAMATIC SIMPLICITY IN ACCOUNTING FOR RETROGRADE MOTION OF PLANETS.
   c) his adoption of noncircular motions.
   d) its explanation of the parallax shifts seen in distant stars.

7. According to Newton's laws of motion, if we see something moving at
   constant velocity,
   a) a constant force is propelling it.
   b) it must be freely falling in a gravitational field.
   C) NO (UNBALANCED) FORCE IS ACTING ON THE OBJECT.
   d) its acceleration must be at right angles to its motion.

8. Among the planets orbiting the Sun, the more distant ones
   a) move at the same speed as the closer ones.
   b) move faster than the closer ones.
   C) MOVE SLOWER THAN THE CLOSER ONES.
   d) are not affected by the Sun's gravity.

9. The point of the Apollo 15 lunar-surface video was that
   a) in the weaker gravity of the Moon, everything falls more slowly than here.
   B) WHERE THERE IS NO AIR RESISTANCE, EVERYTHING FALLS AT THE SAME SPEED.
   c) the laws of motion depend on the local environment.
   d) where there is no gravity, motions cease.

10. Which of these is _not_ a quantity which is conserved in a closed system?
   a) mass+energy.                        c) momentum.
   B) VOLUME.                             d) angular momentum.