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ASTR 101 ch8-9

Question 1 of 42

1

Observations show that interstellar clouds can have almost any shape and, if they are rotating at all, their rotation is not perceptible. However, the nebular theory predicts that a cloud will rotate rapidly once it shrinks to a relatively small size. What physical law explains why a collapsed cloud will rotate rapidly?

Select one of the following:

  • the law of conservation of energy

  • the universal law of gravitation

  • kepler's second law

  • newton's third law of motion

  • the law of conservation of angular momentum

Explanation

Question 2 of 42

1

The nebular theory also predicts that the cloud should heat up as it collapses. What physical law explains why it heats up?

Select one of the following:

  • the universal law of gravitation

  • newton's third law of motion

  • the law of conservation of angular momentum

  • the law of conservation of energy

  • kepler's second law

Explanation

Question 3 of 42

1

The nebular theory also predicts that the cloud will flatten into a disk as it shrinks in size. Which of the following best explains why the collapsing cloud should form a disk?

Select one of the following:

  • colliding cloud particles exchange angular moment and, on average, end up with the roation pattern for the cloud as a whole

  • All collapsing objects tend to flatten into a disk, regardless of their rotation.

  • As a star forms near the cloud center, its wind blows away material that is not aligned with its equator, thereby leaving an equatorial disk of material.

  • Gravity pulls more strongly on material along the rotation axis than perpendicular to it, bringing this material downward into a disk.

Explanation

Question 4 of 42

1

As you've seen, the nebular theory predicts that a cloud that gives birth to planets should have the shape of a spinning disk. Which observable property of our solar system supports this prediction?

Select one of the following:

  • All the planets orbit the Sun in the same direction and in nearly the same plane.

  • The four largest planets all have disk-shaped ring systems around them.

  • There are two basic types of planets in our solar system: terrestrial and jovian

  • The orbit of Earth’s Moon lies very close to the ecliptic plane.

Explanation

Question 5 of 42

1

The solar system has two types of planets, terrestrial and jovian. According to the nebular theory, why did terrestrial planets form in the inner solar system and jovian planets in the outer solar system?

Select one of the following:

  • Denser particles of rock and metal sank into the inner solar system, leaving only gases in the outer solar system.

  • All the planets started out large, but the Sun’s heat evaporated so much material that the inner planets ended up much smaller.

  • Ices condensed only in the outer solar system, where some icy planetesimals grew large enough to attract gas from the nebula, while only metal and rock condensed in the inner solar system, making terrestrial planets.

  • After the planets formed, the Sun’s gravity pulled the dense terrestrial planets inward, leaving only jovian planets in the outer solar system.

Explanation

Question 6 of 42

1

Based on the nebular theory as it explains our own solar system, which of the following should we expect to be true for other star systems?

Select one or more of the following:

  • Planetary systems should be common.

  • Planetary systems will always have four terrestrial planets and four jovian planets.

  • Jovian planets always form farther from their star than terrestrial planets.

  • Planetary systems should generally have all planets orbiting in nearly the same plane.

  • Some planetary systems will have terrestrial planets that orbit their star in a direction opposite to the orbital direction of the jovian planets.

  • Many extrasolar planets should fall into the terrestrial or jovian categories.

Explanation

Question 7 of 42

1

Two hypothetical discoveries in Part A deal with moons that, like Earth's moon, are relatively large compared to their planets. Which of the following best explains why finding 1 planet with such a moon is consistent with the nebular theory, while finding 6 planets with such moons is not consistent?

Select one of the following:

  • The nebular theory holds that moons of any size should be rare, so finding 1 is not too surprising but finding 6 would be very surprising.

  • Unusually large moons form in giant impacts, which are relatively rare events.

  • The nebular theory says that only planets at least as large as Earth can have large Moons, and 6 Earth-size planets would not be likely to form in one solar system.

Explanation

Question 8 of 42

1

Consider the hypothetical discovery from Part A reading: "A star's 5 terrestrial planets orbit in the opposite direction of its 3 jovian planets." This discovery would be inconsistent with the nebular theory because the theory holds that __________.

Select one of the following:

  • all the planets formed in a rotating, disk-shaped nebula

  • terrestrial planets should orbit in a different plane from the plane of the jovian planets

  • star systems should have equal numbers of terrestrial and jovian planets

Explanation

Question 9 of 42

1

Consider the hypothetical discovery from Part A reading: "Beyond its jovian planets, a star has two ice-rich objects as large as Mars." This discovery is consistent with the nebular theory, because this theory predicts that _________.

Select one of the following:

  • this might have happened in our own solar system if it had taken longer for the solar wind to clear the solar nebula

  • ice-rich objects the size of terrestrial planets should exist in all solar systems

  • terrestrial planets sometimes form beyond the jovian planets

Explanation

Question 10 of 42

1

What do we mean when we say that a nucleus undergoes radioactive decay?

Select one of the following:

  • The number of protons or neutrons (or both) in the nucleus changes.

  • The nucleus splits into two equal size pieces.

  • The mass of the nucleus is converted into high-energy X rays and gamma rays.

  • The nucleus emits radio waves

Explanation

Question 11 of 42

1

Suppose you have a rock that, when it solidifies, contains 1 microgram of a radioactive isotope. How much of this isotope remains after five half-lives?

Select one of the following:

  • 1/8 microgram

  • 1/16 microgram

  • none

  • 1/32 microgram

  • Cannot be determined without knowing the daughter isotope.

Explanation

Question 12 of 42

1

Approximately what is the half-life of uranium-235?

Select one of the following:

  • 0.5 billion years

  • 1.25 billion years

  • 2.8 billion years

  • 700 million years

Explanation

Question 13 of 42

1

Suppose you find a rock and measure that 12.5% of the original uranium-235 still remains it, while the other 87.5% has decayed into lead-207. About how old is the rock?

Select one of the following:

  • 2.8 billion years

  • 2.1 billion years

  • 4.5 billion years

  • 1.25 billion years

Explanation

Question 14 of 42

1

Based on Planet Z's size, orbital distance, and rotation rate, which of the following properties is it likely to have?

Select one or more of the following:

  • seasons

  • polar ice caps

  • a surface crowded with impact craters

  • an atmosphere produced by outgassing

  • active volcanoes

  • strong winds and violent storms

  • erosion due to liquid water

  • active tectonics

Explanation

Question 15 of 42

1

You have found that Planet Z should have active tectonics and volcanism and an atmosphere produced by volcanic outgassing. What single factor explains why the planet should have these characteristics?

Select one of the following:

  • lacks axis tilt

  • has a large size for a terrestrial planet.

  • closely orbits its star.

  • has a slow rotation rate.

Explanation

Question 16 of 42

1

In Part A, you found that Planet Z should not have polar ice caps or liquid water. What single change to Planet Z's characteristics would allow it to have these things?

Select one of the following:

  • a greater distance from its star

  • a larger axis tilt

  • a smaller size

  • a larger size

Explanation

Question 17 of 42

1

In Part A, you found that Planet Z should not have strong winds and violent storms. What single change to Planet Z's characteristics would cause it to have strong winds and violent storms?

Select one of the following:

  • a smaller size

  • a faster rotation rate

  • a larger axis tilt

  • a greater distance from its star

Explanation

Question 18 of 42

1

In Part A, you found that Planet Z should not have seasons. What single change to Planet Z's characteristics would cause it to have seasons?

Select one of the following:

  • a larger axis tilt

  • a smaller size

  • a faster rotation rate

  • a greater distance from its star

Explanation

Question 19 of 42

1

Start on the home screen of the interactive figure, with "Elevation is off." Then turn elevation on, and compare what you see. You may wish to switch back and forth between elevation on and off a few times. Then select the statements below that are true. Note: Features such as impact craters that are actually round in shape are distorted into oval shapes at mid- to high-latitudes by map projection effects.

Select one or more of the following:

  • Most of the northern hemisphere has much lower elevation than the southern hemisphere.

  • Several large volcanoes are found near or somewhat north of Mars's equator.

  • There is a long, deep canyon that strectches along a region close to Mars's equator.

  • There is a large, roundish region of low-elevation in the southern hemisphere

  • The northern hemisphere is more heavily cratered than the southern hemisphere.

  • The icy polar caps have the highest elevations of any features on Mars.

Explanation

Question 20 of 42

1

Go to the screen "Key Evidence of Water," and and select the feature called "Recurring Slope Lineae." Study this feature at each of the four zoom levels offered, and be sure to view the animation called "recurring slope linaea (gif)" that you will see at the third zoom level. Which of the following statements are true?

Select one or more of the following:

  • The recurring slope lineae are found among impact craters.

  • The recurring slope lineae appear to be volcanic in origin.

  • The recurring slope lineae look like narrow dark streaks

  • The recurring slope lineae are found on flat ground.

  • The recurring slope lineae appear to grow in spring and summer.

Explanation

Question 21 of 42

1

Go to the screen "Mars Mission Landing Sites," and and select Opportunity landing site (2004). Explore all five zoom levels offered, making sure to read the captions at the tops of the screens. Based on the information provided, why was the landing site,called Meridiani Planum, chosen for the Opportunity mission?

Select one of the following:

  • The region was in the only part of Mars that had not yet been explored

  • The region has very low elevation, and therefore might once have been in an ancient ocean.

  • The region was already known to have minerals likely to have formed in liquid water.

  • The region is near the Martian equator, which makes landing easier.

  • The region was already known to have very small rocks called "blueberries" that likely formed in liquid water.

Explanation

Question 22 of 42

1

Scientists can estimate the age of a planetary surface by counting __________.

Select one of the following:

  • erosion features

  • tectonic features

  • impact craters

  • volcanoes

Explanation

Question 23 of 42

1

According to present understanding, which of the following statements about the solar wind is not true?

Select one of the following:

  • It is even stronger today than it was when the Sun was young

  • It helped in the transfer of angular momentum from the young Sun to particles that blew into interstellar space, which explains why the Sun rotates so slowly today.

  • It consists of charged particles blown off the surface of the Sun.

  • It swept vast amounts of gas from the solar nebula into interstellar space.

Explanation

Question 24 of 42

1

According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?

Select one of the following:

  • The law of conservation of angular momentum

  • Einstein's law E=mc2

  • The law of universal gravitation

  • The law of conservation of energy

Explanation

Question 25 of 42

1

According to our present theory of solar system formation, which of the following statements about the growth of terrestrial and jovian planets is not true?

Select one of the following:

  • Both types of planet begun with planetesimals growing through the process of accretion, but only the jovian planets were able to capture hydrogen and helium gas from the solar nebula.

  • The terrestrial planets formed inside the frost line of the solar nebula and the jovian planets formed beyond it.

  • Swirling disks of gas, like the solar nebula in miniature, formed around the growing jovian planets but not around the growing terrestrial planets.

  • The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.

Explanation

Question 26 of 42

1

Which of the following is not a line of evidence supporting the hypothesis that our Moon formed as a result of a giant impact?

Select one of the following:

  • The Moon's average density suggests it is made of rock much more like that of the Earth's outer layers than that of the Earth as a whole.

  • Computer simulations show that the Moon could really have formed in this way.

  • The Pacific Ocean appears to be a large crater - probably the one made by the giant impact.

  • The Moon has a much smaller proportion of easily vaporized materials than Earth.

Explanation

Question 27 of 42

1

According to our present theory of solar system formation, which of the following objects now reside quite far from the place where they formed originally?

Select one of the following:

  • Kuiper belt comets

  • Oort cloud comets

  • Asteroids of the asteroid belt

  • The terrestrial planets

Explanation

Question 28 of 42

1

According to our theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?

Select one of the following:

  • The law of conservation of angular momentum

  • Newton's third law

  • The two laws of thermal radiation

  • The law of conservation of energy

Explanation

Question 29 of 42

1

The region of our solar system between Mercury and Mars has very few asteroids, while the region between Mars and Jupiter has many asteroids. Based on what you have learned, what is the most likely explanation for the lack of asteroids between Mercury and Mars?

Select one of the following:

  • Gravity was too weak to allow asteroids to form in this part of the solar system.

  • All the asteroids that formed between Mercury and Mars later migrated to the asteroid belt between Mars and Jupiter.

  • There were very few planetary leftovers in this region, because most of the solid material was accreted by the terrestrial planets as the planets formed.

  • It was too hot for asteroids to form in this part of the solar system.

Explanation

Question 30 of 42

1

According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?

Select one of the following:

  • It flattened as a natural consequence of collisions between particles in the nebula.

  • It was fairly flat to begin with, and retained this flat shape as it collapsed

  • The law of conservation of energy.

  • The force of gravity pulled the material downward into a flat disk.

Explanation

Question 31 of 42

1

Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support our theory about how the terrestrial planets formed?

Select one of the following:

  • The meteorites sizes are just what we'd expect if metal and rock condensed and accreted as our theory suggests.

  • Their appearance and composition matches what we observe in comets today, suggesting that they were once pieces of icy planetesimals.

  • The meteorites appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.

  • Their overall composition is just what we believe the composition of the solar nebula to have been: mostly hydrogen and helium.

Explanation

Question 32 of 42

1

Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a half-life of 1.25 billion years. By measuring the amount of its decay product (argon-40) present in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the rock solidified. How old is the rock?

Select one of the following:

  • 1.25 billion years

  • 3.75 billion years

  • 2.5 billion years

  • 5.0 billion years

Explanation

Question 33 of 42

1

All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?

Select one of the following:

  • Venus's largest features are three elevated regions that look somewhat like continents.

  • Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.

  • Venus appears to lack any water that could lubricate the flow of rock in its crust and mantle.

  • Venus has many circular features, called coronae, which appear to be tectonic in origin.

Explanation

Question 34 of 42

1

The cores of the terrestrial worlds are made mostly of metal because

Select one of the following:

  • over billions of years, convection gradually brought dense metals downward to the core

  • metals sunk to the centers a long time ago when the interiors were molten throughout

  • the terrestrial worlds as a whole are made mostly of metal

  • the core contained lots of radioactive elements that decayed into metals

Explanation

Question 35 of 42

1

Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?

Select one of the following:

  • a rapid, up and down churning of the material in the mantle

  • not much - on human time scales, the mantle looks like solid rock

  • dense metals falling downward while low-density rock rises upward

  • hot molten rock rising upward throughout the mantle and cool, solid rock falling downward

Explanation

Question 36 of 42

1

Which of the following is the underlying reason why Venus has so little wind erosion?

Select one of the following:

  • its relatively close distance to the Sun

  • its small size

  • its slow rotation

  • its thick atmosphere

Explanation

Question 37 of 42

1

You discover an impact crater that is 10 kilometers across. Which of the following can you conclude?

Select one of the following:

  • It was created within the past 1 billion years.

  • It was created by the impact of an object about 10 kilometers across.

  • It was created by the impact of an object about 1 kilometer across.

  • It was created within the past 10 million years.

Explanation

Question 38 of 42

1

The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that ________.

Select one of the following:

  • a large baked potato takes longer to cool than a small baked potato

  • thunderstorms tend to form on hot summer days

  • gas bubbles form and rise upward in boiling water

  • Earth contains more metal than the Moon

Explanation

Question 39 of 42

1

The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)

Select one of the following:

  • Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.

  • Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours.

  • Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.

  • Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.

Explanation

Question 40 of 42

1

What are the two geological features that appear to set Earth apart from all the other terrestrial worlds?

Select one of the following:

  • plate tectonics and widespread erosion

  • mantle convection and a thick atmosphere

  • shield volcanoes and plate tectonics

  • significant volcanism and tectonics

Explanation

Question 41 of 42

1

Why is Earth's continental crust lower in density than seafloor crust?

Select one of the following:

  • Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near subduction zones.

  • Continental crust comes from Earth's inner core while seafloor crust comes from the outer core.

  • Continental crust comes from volcanoes while seafloor crust comes from geysers.

  • Continental crust is made from a low-density volcanic rock called basalt.

Explanation

Question 42 of 42

1

The choices below describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)

Select one of the following:

  • Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.

  • Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.

  • Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours

  • Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.

Explanation

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