Download The correct answers are written in bold, italic and underlined. The

Comins DEU 3e Ch 02 Quiz 2 completed
The correct answers are written in bold, italic and underlined.
The most important questions to study for the exam are highlighted.
1. A planet moving in an ellipse with the Sun at one focus will have a speed that is
• constant along the orbit, as required by Kepler's law.
• highest when it is farthest from the Sun.
• highest when it is closest to the Sun.
2. Kepler's laws
• apply universally wherever two objects orbit each other under gravitational
attraction.
• apply only to objects orbiting the Sun, such as planets, comets, asteroids, and
artificial man-made satellites. They do not hold for objects orbiting any other object
in the universe.
• apply exactly only to large planets orbiting our Sun. They do provide an approximate
description for smaller objects (asteroids, etc.) orbiting the Sun, but they are not
applicable at all for other situations, such as mutually orbiting binary stars.
3. If you were to draw a straight line from the Sun to Mars and then watch this line as
Mars moves along its orbit around the Sun, what would you see?
• The area swept out by the line in 1 week would be the same in all parts of Mars's
orbit.
• The angle (measured in degrees) swept out by the line in 1 week would be the same
in all parts of Mars's orbit.
• The length of the line (measured in kilometers) would be the same in all parts of
Mars's orbit.
4. According to Kepler's third law, an asteroid orbiting the Sun at twice the Earth's
distance from the Sun would have a sidereal period of
• 4.0 years
• 2.8 years
• 8.0 years
5. Galileo observed four moons orbiting Jupiter. How did this observation contradict
Greek dogma about the universe to incur the wrath of the established church, which
believed and taught the Greek idea?
• This observation showed that planets other than the Earth had a moon or moons,
contrary to Greek belief.
• This observation showed that there were objects that did NOT orbit the Earth,
contrary to the Greek model.
•
This observation showed that there were objects that did not orbit the Sun, as required
by the Greek model.
6. Which observation of Venus through his new telescope convinced Galileo that it
orbited around the Sun and not the Earth?
• Venus showed phases similar to those of the Moon and appeared largest when it
was at crescent phase.
• He saw it move into eclipse behind the Sun during its orbital motion.
• He noted that Venus always remained close to the Sun in the sky, simply moving
from one side of the Sun to the other over time.
7. Newton's first law of motion, stating that "a body, once given a certain speed, will
maintain that speed forever unless acted upon by an unbalanced force," appears to be
contradicted by everyday experience. Why is this?
• Because friction almost always acts on an object moving on the Earth and supplies
the unbalanced force to slow the object down
• Because we live on a rotating planet, and its rotational motion significantly affects the
motion of objects as they move on the Earth
• Because gravity always acts on objects on the Earth and supplies the unbalanced
force to slow the object down
8. What is acceleration?
• The change in an object's velocity in 1 second
• The total force on an object
• The change in an object's position in 1 second
9. Which of the following persons or objects is NOT accelerating?
• A person standing on a set of scales weighing himself
• An apple falling toward the ground in the Earth's gravitational field
• The Moon moving in its orbit around the Earth
10. Which of the following three objects or persons is NOT accelerating?
• A racecar traveling at constant speed around a circular track
• A skydiver falling in a straight line at a constant speed (i.e., at "terminal speed")
• A water skier slowing down while moving in a straight line after letting go of the
towline
11. A wheelbarrow of mass M kg was transported to the Moon during an Apollo mission.
Its weight on the Earth was W lbs. Which of the following conditions is found to hold on
the surface of the Moon?
• Its mass remains the same while its weight is found to be zero because the
wheelbarrow is at a large distance from the Earth's center.
• Its mass remains the same, but its weight on the Moon is less.
• Its mass and weight are reduced by the same fraction, to 1/6 of their values on the
Earth.
12. An astronaut exerts a certain force on a satellite to accelerate it away from the Space
Shuttle. She then exerts the SAME force on another satellite that has twice the mass of
the first satellite. How does the acceleration of the second (more massive) satellite
compare to that of the first satellite?
• The two satellites have exactly the same acceleration because the forces are the same.
• The more massive satellite has twice the acceleration of the lighter satellite.
• The more massive satellite has half the acceleration of the lighter satellite.
13. A person is pushing (and slightly squashing) a basketball against a wall. According to
Newton's third law, the reaction force for the force that the hand exerts on the basketball
is
• the force that the basketball exerts on the wall.
• the force that the basketball exerts on the hand.
• the force that the wall exerts on the basketball.
14. A moose is standing at rest on a rock. The weight of the moose is the force of gravity
pulling downward on the moose, and the rock is pushing up on the moose with a force
that is equal and opposite to this weight. This is an example of
• Newton's third law
• None of Newton's laws
• Newton's second law
15. Which of the following ice skating couples, skating around each other, has the highest
angular momentum?
• A mixed couple—a man of mass 80 kg and a woman of 60 kg—spinning at one
revolution per second, 1 meter apart
• Two women, each of 60 kg, spinning at one revolution per second, 1 meter apart
• Two men, each of mass 80 kg, spinning at one revolution per second, 1 meter apart
16. Stars that are much more massive than the Sun end their lives by exploding. In some
of these supernova explosions, the rotating core of the original star collapses (shrinks
suddenly in size) to become a very compact object only 20 or 30 km across, called a
neutron star. How does the rate of spin (rotations per hour) of the neutron star compare to
the rate of spin of the original stellar core?
• The neutron spins much slower than the original stellar core.
• The rate of spin is conserved (remains constant) as the stellar core collapses, so the
two spin rates are the same.
• The neutron star spins much faster than the original stellar core.
17. In which of the following situations would the gravitational force from the Earth on 1
kg of matter be equal to zero?
• A 1-kg mass orbiting in the Space Shuttle
• A 1-kg mass at rest on a smooth surface of ice on the Earth
• 1 kg of matter at the center of the Earth
18. Which of the following masses would feel the greatest gravitational force from the
Earth?
• 150 kg on the surface of the Earth, 6400 km from its center
• 600 kg, at a distance of 3 Earth radii from the Earth's surface, or 4 radii (25,400 km)
from its center
• 300 kg, at a distance of 1 Earth radius from the Earth's surface, or 12,800 km from its
center
19. The Earth exerts a force on an artificial satellite of mass 1000 kg. What will be the
size of the force exerted on the Earth by the satellite?
• Exactly the same as the force of the Earth on the satellite
• Very small compared to that on the satellite because the satellite's mass is very small
• Zero because the satellite's mass is negligible compared to that of the Earth
20. Nuclear fusion is a process by which
• grains of dust and ice collide and stick together to form the nuclei (inner cores) of
planetesimals.
• the nuclei of heavier elements split apart into lighter elements.
• the nuclei of lighter elements combine together into heavier elements.